When I had the LS6 built for my 70 Parisienne it cost me way more than the LS4 in my 70 2+2. In both cases I provided the entire valve train, with the exception of the valves, but I had additional machine work done on the LS6 (changing it from an 2 bolt main LS4 to 4 bolt, and added the fitting for an oil cooler). So, be prepared.