I have used them many times....never had a problem and the few people I know that have the warranty is solid as a rock.
Recently I found a guy who will build a 383 about 425 horse for $2200. Just got the first for us ( he has been doing it for years) and will have it in soon.
Block is used but everything else is new. Block is cooked and decked. You need to supply water pump, carb and dist.. Heads are stock. Everything I have heard is very good with this guy and will warrant it as well. Near Carlsile so not to far from you. Let me know if you want the info.
But I think GM is a great way to go