Is it safe to assume that you know that the 71 B body 4 speed bench stuff is all unique. So if you are short any parts, then going with the bucket seat/E body set-up would be the only real option because there isn't much available for the bench seat set-up. I don't think that even the boot for that set-up is available, is it?

And the fold down arm rest cars came with the same set-up that the bench seat cars did.

I think that the bucket seat/E body shifter set-up will be coming up through the floor right into the arm rest.

If you do decide to swap set-ups and have all the stuff from the bench seat set-up, it is probably worth a good bit of coin. Some of that stuff is nearly impossible to find.