LT1's were available in the B Bodies (Caprice, Impala, Roadmaster, Cadillac Fleetwood, Olds Custom Cruiser) from 1994 to 1996. Some cars got the 5.7 LT1, while the rest received the smaller 4.3 L99 "baby" LT1, both with iron heads.
What you have is the L03 305 V8, which uses throttle-body injection, while an LT1 is fuel injected (MPFI). An LT1 swap can be done but, from what I have read on the Impala SS forum, it is cheaper to just buy an LT1-powered Caprice.
You do have an interesting project on your hands and I am wondering if the other members could give some input on the tuning of TBI systems.