You need to pick your unit carefully. GM made a lot of these and some of them aren't very strong. I'm using one from an '85 Monte Carlo 5.0 (non SS) between a mild 292 and 3.50 geared 9" Furd and couldn't be happier.
I sent you an E with the info I have.

JOE
II# 3486
'48 FLEETLINE AERO

http://s639.photobucket.com/albums/uu117/lars62go/