Question about SBC

[72shorty]

I currently own a '72 with an L6 and 3spd on the column. I have just purchased a 700R4 tranny and eventually want to swap to a 350 SBC. HOWEVER, I am broker than broke after making several small purchases for my new old truck. So, my question is this: will my L6 pull that 700R4 ok AND how big of a hassle is it going to be to only swap the tranny now as opposed to doing it ALL later?

Any insight is much appreciated!