Engine mounts
While not an A body, my B body small block to big block swap required a cutting of the stock perch, which was quick & E-Z! Sooo non regrettable.
I have not done a s/b to b/b in an A body. Considering the instructions of the creative swaps made it so easy and clean, I'll never do a K frame swap.
One last thing about small to big swap in an A body, the BB K frame is an ultra rare K frame.