The 400 small block & 86 up 350,s use balance weights in the flywheel. They will work if you use the corresponding flyweel. The weight should not interfere with anything. The 400 has overheating problems & would not work well in something like that. The bolt pattern is the same plum up into the 90,s. You may want to look at a big block. They bolt up the same. I believe it should have a big enough radiator for a 350.
