low gearset 904?

i used to know all this **** but it was so long ago since i thought about it i've forgotten most of it.. uw put a liw gearset 904 in my buddies 66 barracuda and it works well.. that thing has a stock long block, hemi gring cam and a street tunnel ram with that low gear 904 ans a 3.23 gear. damn thing runs mid 12's and he can drive it anywhere..