Listen, I know some of you are gonna hate me for saying this, But I once got my HotRod 367 combo up to 32 mpgs. and it still got into the 12's with 245 tires, spinning most of the way.
This is not a brag.
This is a statement of fact.
and it was running 3.55s with an A833d and a GVod behind that for, Seven useable and sequential gears-ratios.
The trick is to know your engine, and feed it the ignition advance it so desperately needs at low rpm.
With this combo, the ratios were
3.09-2.41-1.67-1.30-1.00-.78od-and .55 od
With 3.55s; 65= 1590 rpm, 75=1840, 85= 2060
The ignition timing needs to follow.
In my case, it required high 50s to low 60s, depending on the cruising speed/rpm. After that, I just leaned out low-speed circuits, until is began to hunt, then threw a lil fuel back in.
But, getting back to the question, I have nearly always had, since 1970, a 4-speed A-body in the driveway. and for the most part, they have always had 3.55s, in fact my current 3.55s may have been out of that 1970 Swinger 340. and, for the most part, I have always run the tallest tires that fit on the car, usually around 27/28.
But I have always hated cruising those 3.55 gears cuz 65= about 2900, even with the current combo which is very well balanced. About 10 years ago, I got me that GVod, and so with the latest trans combo, she cruises at 65= 2240, still with the 3.55s. ....Which is infinitely better.
I would and have cruised at lower rpms but, that iteration that cruised at up to 32 mpgs, dropped lobes in 2004. The cam that replaced it, can't touch that 32 mpgs no matter how hard I have tried. So, the 3.55s get me to 65=5520 in Second, or to 60=6400 in First-over, which is fairly ideal, so, the 3.55s have stayed.
But man, those gears are tuff, I bet they have a half a million miles on them or more.
BTW, I have tried nearly every combination of rear gear that Mopar makes, with every fine-spline A833 she makes, and I can tell you that no matter what I ran, a starter gear of about 11/1 is all my HO-6liter ever wanted, and not any more. down to 10/1 with this latest cam is Ok too. but no less than 9/1. This is not for lack of power mind you, but the slowest my engine will idle in gear is about 500; which with 3.55s gets me 3.6 mph, to parade at. Any less gear will just increase the slowest speed higher than I want to idle around at.
With an auto trans, obviously, this is not a consideration for you.
BTW-2
I'll never run 3.55s again without an overdrive. I have never liked it, and at age 70 now, I can't imagine cruising at much over 2200 ever again. When I ran 3.55s alone, I usually ran at about 55= 2450
