Welcome Kami,
Good luck! I did the same V8 to 250 inline six in a '65 Impala. I suggest obtaining the entire 6 cyl mounts. Your experience may vary, it was not a direct bolt in for me, at 16. The mounts were different. Usually, Chevy is not like this, but the bottom mounting plate to frame for my application was different. No problem. Ordered the parts from Chevy. 1974. It well well. By 50%.
After Chevy sent one same side mounting plate wrong 3 times, Chevy parts guy threw up his hands and said sorry Son. I chained down the motor on the high side and let 'er rip. That was after I figured put I'd better do that because the motor would lift and disconnect the shift linkage at the Powerglide.
Computer was no issue for me, V8 TBI, onto that I-6 will be interesting.
Good wrenching!! We're here to help. This is a good one!