x2 on the carriage bolt. I was not able to find a Metric sized carriage bolt at my local ACE hardware, so I went ahead and used a 7/16th standard size. It fit nicely into the frame.
As for checking clearance between the bolts and the radiator, no I did not check clearance. I did, however, take a grinder and thinned out the top of the bolt to resemble the flat top of the OEM toyota bolts. Unsure how the carriage bolt fit before.
Down below is my original radiator support. its from a 1971 fj40. Notice how the bottom corners are curved. These curved parts and the current mounting holes (drilled into the chassis) are whats preventing you from sliding it any further toward the grill.
Down below is a 73+ radiator support. Notice how it it is cut at an angle VS the rounded corners of the earlier year. This angle will allow you to slide the radiator support further toward the grill once you drill out new holes into the support. Without the cut angle, it would hit against the front of the chassis with the rounded corner.
You can either grind down your early radiator support corners to have the cut angles on both sides to resemble a 73+. Or, you can source out a 73+ support on ebay or Ih8mud.
once you have the correct angle for the radiator support, cut off the existing bolts and drill out some new ones about a 1/2-inch further. I think I did mine about 1/4inch and its still a bit too close to the fan....however its not very far off. Make sure to measure 3 times before just to make sure you get the clearance that you want.
here is how my fan relates to the fan shroud. it's around 3/4 of the way into the shroud vs the "desired" mid-point.
clearance between my fan and radiator. In my father's 78 fj40 (stock radiator setup), i'm able to stick half of my hand into the gap of the radiator/fan. In my set up, im only able to slide my hand up to my "punching knuckles". Just to give you an idea of how much more clearance I needed to get it "just right."
