your gona need a set of pipes , shearers or cpis for that cub a 4mil 68 bore 421 cub is a wicked motor . it will need those 38 carbs or 35s work well
i ran mine stock trans set up with shift star and it shifted fine . also ran all 6 rdz springs to hold the clutch ,and i ran shearer inframes .you will need some serious tires for it to ,it will rip off knobs and roast a set of tires before you can even let off. the supercub reguires case boring and only makes about 5 more hp than the 68 and in imo its not worth the extra money it cost oh and it takes a diffrent head to .
first thing i would get rid of is those fmf pipes .