Parts are the problem. If you have parts in hand and have cash up front then shops can fit you in. If you can't find anyone local call Gray's Automotive down here in Oregon. Or Portland Engine Rebuilders. If you don't have parts and you expect the engine builder to order the parts for you then you might be looking at a 6 month wait.

Paul at Gray's is building engines all day long every day. He has several BB Mopar strokers engines going together right now. Last time I was there he had a 451, a 470 and a low deck 512 on the floor. I helped him run a SBC 427 on the dyno. Fun engine, made around 550 hp. Street engine so it will surprise some folks.