Old style V8s are going to suffer in the fuel mileage world vs. the LSx motor. He can pay now and get good fuel mileage or pay out the ass for gasoline. LS2 all the way bro. Otherwise, LS1, 6.0L, 5.3L or 4.8L in that order. The cast iron engines are a dime a dozen, except the LQ4/LQ9 6.0s. Any 5/6 speed will fit them all, you'll just miss one bolt hole. Unless you're putting out 500 hp I wouldn't worry about that. I'd go with the T56 though for simplicity, no adapters required for the cranshaft. The standard trans for the LSx Vortecs are getting more plentiful in salvage yards. Try Bishop Automotive in Dallas for an engine core or complete. 214-426-9739. They get Aussie LS1s and sell them minus the harness and PCM. Hiway Auto advertises he has LS1s sometimes. Haven't seen him online much lately posting, though.