He didn't but since he has a 700R4 and the big block had a turbo 400, if he is geared correctly now, it will probably be too low for the big block to be a good freeway car.
Hell I see guys on here with 3.23's and 3.08s behind OD's all the time,(although I honestly wonder what the hell they are thinking) so that doesnt mean anything on here.
I passed on a free Pontiac 428/400 Turbo, AND the '69 Gran Prix SJ they were STILL in 5 years ago. The guy had bought the car from 15 years before that, and thought I might want it back. I passed because it was rough, he hadn't had it running in several years, and I didn't have a place to park it, nor a use for the engine/trans. Of course, a week later I bought the '51 Pontiac wagon, minus engine and trans, by then he'd found someone to take it off his hands. Sigh... Glad it's working out for you!