Thinking about getting a new chunk…

I found a 741-case 3.55 sure-grip center section on craig's list selling for $400.
I'm just wondering if this is a good deal, and will I notice much of a difference if I put it on my car? Let me give you the ol' stats:

71 Satellite (pretty heavy)
360 bored out 60
Holley Street Avenger 670 cfm
Eddy performer intake (the real low-rpm one... with the spreadbore inlet...)
hedman hedders
Mopar Electronic Distributor with orange box
Mild Crane Cam
4 speed OVERDRIVE a833

... all coupled to 2.76 open gears. :o

I was originally thinking I should go for a higher gear (say, 3.91 on account of my OD trans) but this 3.55 has presented itself and I'm tempted. Especially with the sure grip. So is this a good deal? Should I get it, or hold out for a higher ratio? Or is this a good ratio for my set-up.
Author: jenkins71