that's the whole point of finding a complete car, station wagon or truck with big block. You'd have everything there including core support, radiator, shroud, brackets, fan, viscous drive, etc., etc. If you think you're gonna be ahead of the game as far as gas mileage, you might want to think again. To make "x" power, it's gonna take the same amount of gas, whether you're running it through a small block or a big block. A big block just doesn't have to work as hard to do it and you don't have to spend as much money to get there as you would on a small block. Do a stock rebuild on a 402 with a slightly bigger cam and a 2,500 stall converter and it'll bolt right up to your TH350. Summit sells a Hughes converter for $159.95 that would work great with a mild cam and your stock rear gear.