What’s the difference between a LT1 Engine and Chevy small block Gen II (LT-based engines)?

The LT1 engine is the 5.7L gen II engine. You have both. There was an LT5 DOHC engine for 1 year in a ‘Vette, and an LT4 was made with a hotter cam and bigger intake. That was all there was for the LT (gen II) series of small blocks. In 1997 the Corvette got the LS series engine, which was all new. In 1998 the Camaro and Firebird got the LS engine, and the LT engine faded away into obscurity.

1993 was the first year for the LT engine series.

An LT1 is the old tried and true Small Block Chevy, with some improvements like reverse flow cooling and distributorless ignition for example.

The LS1 series all the way up to LS7 is barely a SBC. The block is way different. It is aluminum , except for the truck engines, they have a girdle that comes down further past the crankshaft and strengthens the whole block. The heads are also aluminum and have cathedral shaped ports that flow a ton of air. The ports are also evenly spaced unlike the SBC of yore.

The LS engines are so different that you need a different cross member up front, but that is available for your Camero as they came with LS engines.

The LT series of engines is very good and can make a lot of HP. Do not ignore them as they can be very fast. and they are cheap to improve, being the SBC and not the LS engine.