I have gone the route of the FLAPS rebuilt with warranty that wasn't much difference in price than a new GM crate, but at the time a couple hundred bucks saved seemed big and the warranties were similar. I installed it myself with a friend and had my mechanic do the final tuneup and inspection for warranty purposes. 2 years later I am glad I did as a blocked cooling passage in one head finally caused a crack that filled on cylinder with coolant and hydro-locked the engine. The FLAPS don't warranty rebuilds, the re-builder does. It took the threat of going to small claims court by the mechanic to get the FLAPS to force the supplier to honor the warranty. A GM crate is honored by GM and can be installed by any of their certified mechanics, not just the dealerships. That is the route I went on my next engine.
IF you have a good salvage yard close by you may also consider a takeout engine.
