Ballpark Gear Ratio

If it helps, I just made the switch about 6 weeks ago in my avatar car. Went from 4.56 to 4.10's. Engine is a 408 w/ Eddie RPM's mild porting, 251/255@050 cam, Super Victor, 850DP, 10.5 cr. 28x10.5W bias slick w/CalTrac split mono leafs. 5000 stall 8" ATI Treemaster converter. Cage, subframes tied. Weight unknown but guessing around 3400 with me in it. The car was not 100% dialed in (and still isnt!) but close enough for this topic/comparison.

The 4.56's wanted to trap in the 6700+ rpm area and I know this stroker motor's power peak is somewhere in the 5700-5900 range. So that rpm is too high. Best was an 11.31 @ 115.

Swapped in the 4.10's. At roughly 1000 worse DA (roughly 3000 DA), the car has now run an 11.25@117. It traps close to 6200 now - exactly where I hoped it would. I share a little running log of the car in the thread "The 72 Demon Follies...".

Note that I use a spool with both ratios. The suspension works really well so tire spin has not been an issue with either axle.

IMHO...I would go with a 4.10. I doubt many of us (certainly not me!!) will ever reach the power and chassis expertise that GTX JOHN has in his cars hence a little more axle than his 3.91 may help. My $.02.