I find motors/trans on ebay all the time for fairly cheap, the thing is most of them are out of the cars and I don't know if I would really trust them when they say how many miles are on them and how it runs. I've been looking too cause I'm trying to find a deal on a block to start building my next motor.
I'd say your best bet really might be to just straight up buy an lt1 car, you can get one for a steal nowadays especially since your looking for a project car.
And you know who to call once to start the project lol