There is no such thing as a "Standard" C4. Externally they all look pretty much the same but on the inside there are some major differences. Clutch drums with 2 to 5 clutch friftions ( the more you got the better it is) The C5 case has better oiling and cooling than any of the C4s. You have to use a C4 valve body on the C5 to make it as strong as the C4 and you can't use the lock-up converter so you need one from a C4 that matches your ring gear. Same with the bell housing you will want to match it to your ring gear. Typically C4s made for V8s have five forward clutches and four direct clutches. You are puting it behind enough engine that even in stock form a V8 C4 is marginal "as delivered" and should at least be fitted with a TransGo -2 kit for the valve body and a big transmission cooler. having it further modified could make it substantially stronger but not necessary for a stock 351 street engine. The C4 that you have might be rebuildable at less cost than a new transmission is going to cost you. The transmission parts house that I deal with sells new transmission and have a shop next door that can supply them with rebuilds for customers. you buy transmissions through a lot of on-line and E-Bay businesses. Be aware that getting warranty issues taken care of is easier when the guy who built it is just down the street from you.