Just installed a Richmond 3.55 w/Eaton Posi unit to replace the factory 2.56 open (car came w/Glide , now has M21)
All the difference in the world in "around town" driving. Scoots off the line great and runs at the base powerband @ 35 in 3rd. Gets on the pipe and pulls hard with about 500-700 more RPM (or at 40mph) from a rolling 30-33mph.
(mostly from the cam , but from a gear standpoint)
Runs about 3200 on the highway at about 70 (speedo not ironed out yet ,but paced by another car on the highway). Not too bad on the revs , I and it can definately live on the highway.
I almost bought the 3.73 , glad I didn't , but that's only because I plan on long trips with the Vintage A/C cranking. I think the 3.73 would be neat , but not for me right now. But , if it was a 200 mile day-tripper , or mostly in town , the 3.73 wouldn't be out of the question at all. I had a 3.90 / Muncie car a few years ago and it wasn't very pleasant on the highway , but great in town (gas sucker , but aren't they all ?)
So in my opinion , depending on your displacement , cam & highway needs , the 3.55 is just about the perfect all around gear. I'm happy with it anyway , made a hot rod out of my slug.
(*also keep in mind this is a small block A/C convertible in full RS trim , so it's a tank , base cars & stripper big block coupes would see a far greater benefit)
(3 DUDE give me a call or email me if you see this , about JVille)