if youre going to go for a 4A engine, go for a G-head, the F-head is the gas saver version of this engine, the 4AF has a 15degree valve angle, and the G-head has a 45degree valve angle. not to mention aluminum pistons and hardend crank shaft stock. i have one in my GTS and i love it, the difference is like night and day, especially with a webber carburator