A SBC would probably be cheaper to do, and if you've never done an engine before you will find more tech support for a small block than a turbo Buick. Plus almost any parts house has Chevy parts for cheap, but not so much for a TR. I don't get the reason for a 305 though. Why not go for the extra cubes and do a 350? Hell, you can buy a new 4 bolt main long block with a warrenty from Chevrolet almost cheaper than you can build one after machining costs, new pistons, rings, cam and bearings, ect. On top of that, since the 305 bore is smaller, the valves are shrouded compared to a 4" bore. Neither will pull like the Buick though. What is your budget? Unless you already have a complete Buick set up, be aware that the little detail things quickly add up to a lot of money, particularly if you want to go fast. Fuel pump, adj. FP regulator, injectors, 3" DP, alky, turbo upgrade, ect., ect..