I had 350 after I installed the 454, broke fairly soon, rebuilt is myself, did untold burnouts, sitting in the shop, as I am going 4l80e. Could look at my build, I have it documented.
https://www.gmsquarebody.com/threads/1973-k20-350-to-454-swap.29840/page-7
Post start, 98. Buy an ATSG book...