If it has the circular air filter on the top of the engine, than it's not a LT1, or LS1. You have a carburetted engine (or maybe throttle body injection). The guy you bought it from is either very misinformed, or is feeding you a long line of Bull.
If the distributor is within 2 inches of the firewall, then it's a JTR, if the sits high and forward, then it's a SCARAB.
Tim