6 to 8 Cyl.

The /6 radiator wont do the job well enough to keep the engine cool, so that'll have to go. Also the handling is going to be sloppy unless you replace to torsion bars (although if youre only going to be drag racing the /6 bars will work fine). The transmission bolt pattern is different between a /6 and a small block. Also the 7 1/4 rear you have now probably wont live very long behind a 340, and lastly you'll be adding a lot of weight to the car, so you probably want to upgrade the front brakes to discs if you currently have drums. Hmm it seems like I'm forgetting something but thats the major things I remember right now.