Regardless of what motor you have decided to run, you will still have to throw some more money at that 4-speed. You are going to HAVE to buy a scattershield. A blow-proof bellhousing is a must. You will likely need to rebuild, and strengthen your clutch linkage. You MAY need to buy new linkage pieces to accomodate the scattershield as well. You will also have to get a solid clutch/pressure plate, and I'd go with a new flywheel to be safe. The 4-speed will have to be rebuilt, or any weak links will fail. Also 4-speed guys tend to put alot more gear into the rearend to get the drivetrain to move along easier on the launch... this will help with parts breakage. By the time you take care of these basics you will likely be into it for more than a rebuild for an auto. Racing a 4-speed is a spendy hobby. good luck.