https://i.postimg.cc/8PhK5GS7/IMG-2617.jpg

 

I did a similar swap on my '79 C10. I swapped the 305/TH200 for a 350/TH350 and everything fit perfectly. The TH400 is definitely going to require some fab/modding. You might try looking for a wire harness for another model vehicle, like a Camaro, with the same engine & transmission that you are putting in.

 

What rear ends from GM will fit the 87 monte that come with disc brakes already and handle 450ish HP?

 

....also, Is it worth going to urethane bushings? Or is it too much of a stiffer ride? Or......?

 

For the rear differential question. The only direct replacement I know of is the 8.5 in the Grand national and a few other car's. For the disc brakes you can just do the conversion from the newer s-10 or aftermarket kits

 

So I posted this question earlier in this thread and was hoping for a "better" answer. There are no vehicles of any makes that can be swapped in to the '87 monte with little to no modifications that is stronger than the stock rear end not including the GN's or other probably limited available and therefore a pricey item? I don't have the budget to buy any of these new aftermarket ones I've read here and elsewhere. I'm going to a swap meet this weekend to have a look around but I don't know specifically what I'm looking for. I was going to take some dimensions and photos of mine with me and hope for the best. Doesn't sound too promising of a strategy though.

 

As mentioned before the rear out of a Grand national ( 8.5 ring gear) is a close to a no modification change is one of the he easiest. Only require's a different driveshaft , and you only need to update the brakes since you want rear disc. The stock 7.5 rear will handle the 450hp range in power your suggesting, I can attest to that in my car. You can also visit a local race track and might be able to find a used Ford 9 or 8.8 inch from a G body. Any way you decide will probably run $1000 unless you just upgrade the stock differential.