build a teen, same power as a Commando 273-4 and almost free. 360 alone will have balance issues, 340 is too much money and has a different motor mount location, everything else doesnt fit (good) and I have put a 451 in there. 318 will bolt in 100% and are neutral balanced so you can use your old tranny and convertor, just pick up a adapter ring from Tflite-patty if newer than 67 crank. These cars are light and 340-360's lighting up the tires through 2 gears (yes...) is overkill. Drop a 4bbl Performer on it, dual exhaust, 5-600 CFM 4bbl and some 3.55 gears and youll have a fun car. Been there...still doing that!
273-4
318
340 +.060
340 std
451
403 stroker+efi
225 turbo
225 turbo+efi...in that order...!
