Blueprinting a 3-Way 70 Series Mashup: Modern 76 Front/Drivetrain & LJ78 Body onto Vintage HZJ77 Chassis

[SeanLJ78]

Hi everyone,
I am embarking on a major, ground-up chassis swap project and need some technical guidance from anyone who has navigated the structural and dimensional differences between different generations of the 70 Series family.
My Ultimate Goal:
I am building a custom rig using a 1990–1996 HZJ77 Heavy Duty chassis as the base platform. I need to retain this specific chassis to comply with local vintage vehicle registration and tax laws here in Ireland as the cost difference is into the thousands annually on top of extremely high registration costs

The Donor Setup I Currently Have:
Right now, I have a complete, driving 2009 76 Series (1HZ drivetrain, widetrack axles, gearbox, wiring, and 2007+ "wide-nose" front clip with extremely low mileage) that has already been seamlessly lined up and fitted with an LJ78 Light Duty (Prado/Bundera) cabin by a previous owner as a build that wasn't quite finished.

I now need to completely strip both rigs to the bare frame and transfer the entire 2009 running gear, 2009 front panels, and the LJ78 body over to the older HZJ77 narrow-nose chassis.
I am breaking this build down into three major fabrication stages and would love to hear from anyone who has done parts of this swap successfully:
1. Front Clip & Chassis Width (Narrow-to-Wide Nose Conversion)
Since the HZJ77 is a narrow-chassis frame and the 2009 front panels/bumper are built for the wide-nose V8-era profile, what is the neatest way to fabricate the front frame outriggers?

• Does anyone have the exact millimeter difference or drawings showing how far out the 2007+ front inner aprons and radiator core mounts sit compared to a pre-1999 frame?

2. Suspension & Axle Transfer (Coil/Leaf Conversions)
I am transferring the complete 2009 wide-track front and rear axles over.

• For the front: Has anyone successfully cut the coil towers and radius arm mounts off a post-2007 frame and welded them onto a 1990s HD frame? Are there any steering box clearance traps I need to look out for?
• For the rear: Did you have to relocate the leaf spring hangers on the HZJ77 frame to line up with the 2009 wide rear axle perch widths?

3. LJ78 Body to HZJ77 Frame Mounts
The LJ78 cabin is currently sitting on the 2009 frame. When moving it to the HZJ77 chassis, how drastically do the body puck/mounting tab locations differ between the Light Duty (Prado) body floor pans and the Heavy Duty chassis rails? Is it easier to slice the mounting tabs entirely off the HZJ77 and custom-weld new ones using measurements from the 2009 frame?
If anyone has build threads, frame dimension diagrams, or photos of how they tackled the narrow-to-wide nose outrigger fabrication, please drop them below.
Cheers!

 

[mjw4]

All I'm gonna say is @SNLC

 

[dogfishlake]

Very cool build. I would love to do the same thing, excepts add in LHD.
I have a LHD front frame cut off from a late 76 series (wide/coil/radius arm front) from @bdyer12 that I believe originally was sourced by @joekatana from Europe. I had ideas of putting it under an HZJ-73 mid wheelbase truck I have. The 76 frame is not only wider, but the frame rails themselves are a larger box. I also have a 79 series frame that looks very similar to my HZJ-73 frame- in box size at least, but I have not measured it closely. Strange, that I would think the two would be the opposite of what they are. It isn't an impossible project, and certainly would be a great product when you are done. Really I would think you just build the front axle up with the arms attached to it and line it up under the front of the 77 frame with the body locating and start with the CAD (Cardboard Aided Drafting )
I'm looking forward to your progress, and what other more competent fabricators than myself have to say!

Sláinte

 

[AirheadNut]

Sounds like a really cool project! @BiffS might have some good intel on chassis differences too.

 

[BiffS]

Oh boy...

Yes, I DO have a lot of insight into this sort of swap.
.the 76 frame will be between 10-50mm wider than the 77 frame will be, especially around the frame horns in the engine bay.

Front mounts for the rad support are slightly different heights and locations.

Holes for the fender inners to the the firewall: top and bottom holes may align, but the middle 3 won't. (Off by 1/4-3/4")
The 76 frame is fully boxed and thicker/ slightly larger height and width in places.

The body mounts from firewall back ***should*** be virtually identical to the 77 and 76 as the body shells use the same parts across the years.

Other than that, wiring LHD and 24 volt from the 77 will be the biggest pain point of the swap.

Firewall is different between the generations, especially if you're using plastic dash.
Steering column different if using plastic dash versus steel.

Does that cover it all?

 

[SeanLJ78]

Thanks so much for your reply.

The current dash is from the LJ78 so steel dash ATM.
The steering column was originally a LHD but was swapped over by 4x4 specialist prior to my purchase.

Is there going to be major fabrication work to install the springs on the front of the 77 from the 76 I have and also I've researched a bit and found info on the rear leaf suspension from 76 also being wider and will not line up with the 77 chassis?

 

[SNLC]

All I'm gonna say is @SNLC

Thanks but nah, I don’t want to write a book on how to do this work. Every build is different too. We also don’t do things how most people do, ie we do internal sleeves when we stretch or shorten a frame.

Cheers