Installing an 81 hardtop onto my 74 (keeping the hatch)

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There seems to be a lot of confusion about hardtop compatibility. Detailed here is my retrofit so others may know what's involved. Please be patient... progress has been slow.

To start with: Factory Hardtop July 1974 with rear hatch.
Donor top: 1981 Bj42 (??) Canadian model.
 
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The Glass top.


The header bars at the top of the windshield were different. I swapped in the older one to get around this problem. The offset on the older one is apx 3/4" and the newer one 1" (the rusty one).

The hole spacing is also different and there is no provision for the wipers at the top of the windshield in an 81 hardtop.
 
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The sides themselves are the same size in every respect. In the past I've cut out the cross bar and installed older style windows. Others have stated that they have added the crossbar to be able to install the kick-out windows into their older tops.

I've now got the newer glass top sitting in place with the older header bar... it fits just like the original 74 top. Once I install a headliner it will need to all be bolted together and Riv-Nuts installed to mount the strikers and struts...

More pictures to follow.
 
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The header bars at the top of the windshield were different. I swapped in the older one to get around this problem. The offset on the older one is apx 3/4" and the newer one 1" (the rusty one).

The hole spacing is also different and there is no provision for the wipers at the top of the windshield in an 81 hardtop.

Is the 81 on the bottom in your picture?

It looks like mine including the rust!
 
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Is the 81 on the bottom in your picture?

It looks like mine including the rust!

Yes, the 81 is in the bottom (it's somewhat bent, rusty, and mangled). I used the 74 (top) one so that I'd have an original fit with the windshield.

The holes on the 74 header bar were slotted out years ago to make it easier to remove and install the hardtop.
 
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Pictures


Here are some pictures of the 1981 top installed on the 1974 tub with the 74 hatch.
:cheers:
 
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Still need to paint the hatch to match.
 
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Latch


I've read that the latch can interfere with the stock roll bar. Wasn't a problem with my modified cage.
 
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I am doing a top install as well and an 81 top with the vent windows. My rig is a 78 with the older windshield frame (wipers at the top). My problem is the front bar protrudes 1" over the windshield and if I line the bar up with the windshield there is a gap at the top of the doors because the windshield frame is too far forward and if I line top front up without the door top gap the back over hangs almost like the top is 1"too long for the truck and the oem top mount wipers are cramped to the point that I can barely install the wiper arms. Mine does have the oem roll bar and it does cause a pronlem with the rear vent windows, you can't open them coz the latch is jammed. Did you have a similar problem with the top length or others?



Thanks,
 
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Top length

The fiberglass tops (74/81) were identical in length and width. (About 18 years ago, I replaced my 74 rain gutter with one off a 77 top.) The header bar over the windshield is about 1/4" further forward due to its design than the 74. I swapped in the 74 header bar to avoid a problem due to this.

The sides are identical in dimensions, so I'm not sure why you have such a large gap. Something dosent seem quite right about the way things are fitting. The difference in tops only accounts for 1/4" of your 1" difference.

Since i haven't seen the truck, I'm going to ask you a ton of questions to try to understand what's going on.
Could your header bar be bent forward? Could someone have moved it forward? Is the front of the windshield in a straight line with the top of the cowl (not leaning back too far)? Can you take a measurement from the top of the windshield to the back of the tub (at mounting lip for hardtop)? Could you take some pictures to show: the header bar on the top (in particular how it lines up with the front of the gutter, how it fits the top fits to the windshield, gaps at doors, side view of truck, and any others that might help us to understand why you're having problems. What condition are the body mounts in (could your tub be sagging)?
 
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I will be doing this myself soon on my 71 so this is good timing, thanks for the post!

i will probably be making my own rear hatch as I am in the uk and they will be very very rare!

:cheers:
 
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windows

not sure what it will come with cause a guy on a forum over here is holding it for me---I line both the vent and the sliding windows so we will see---plenty of time for that

thanks
 
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Thanks for your reply Smurf. It could very well be some one at one time moved the front header bar. The body mounts are in good shape but I will do as you suggested and take some tub measurements. I will try to take some pics and post them as well. I too have the rear hatch because I like the way it looks and to me seems more secure.
Thanks again will be back to you asap!
 
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Found the problem Smurf thanks to your suggestions. The front header bar had been moved ahead 1" for some reason not known. It was hidden under the headliner and old holes plugged. Will let you know how it fits after I put it back on.

Thanks again!
 
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Found the problem Smurf thanks to your suggestions. The front header bar had been moved ahead 1" for some reason not known. It was hidden under the headliner and old holes plugged. Will let you know how it fits after I put it back on.

Thanks again!

No worries, glad to hear you found the problem. Strange what some previous owners do.

I generally don't have anyone else to blame... Bought my 40 in 1991, mostly stock, and very rusty. I have to admit I did some strange things when I was 18.:D
 
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Striker and Strut mounting


Pictures of the old hole locations:
 
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more pictures.


Vertical measurements from bottom lip, horizontal from inside of top :
 
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