3 speed or 4 speed trans?

In 1970, Mopar made their 3-speeds stronger than the previous version. This enable them to be used behind 340 & 383 engines as the base trans in cars with 4-speed & auto optional. You could have even got a C-body with the 383 with a 3-speed (on the column of course). So to answer your question, Yes it should be able to handle 350hp but I wouldn't push it pass 400hp.