Don't bother with 4.88, go straight to 5.13 with a 2.5 and 32-33's.
Edit: I see you already bought 4.88, I'd call them and see if you could have them do 5.13 instead if it isn't too late. Seriously, you wouldn't regret it. 4.88's and 33's is still not as peppy as stock, since stock was 27's.
I've done the math on this keeping several considerations in mind.
1. On paper, the 4.88s put me just a tic higher in the revs (about 100 RPM @ 60).
Rolling resistance and tire mass not considered, it's probably a wash, maybe a little less power.
2. Since I'm back in the same RPM range as stock, the speedo won't need a new gear.
Not a big deal, but one less thing I have to do on a list that has gotten WAY too long.
3. Most importantly, I have to drive the Interstate to go anywhere, or I have to Wheel there.
I don't want to be revving a push-rod motor past 3500 for extended periods of time.
3500 is right about where it will be @70 so I don't get run over, w/5.13s that's closer to 4000.
I love a low gear too, would have put in 5.89s if they made them for a 30HP and run 35s, but I gotta be practical.
The old flatty I had, had 5.38s with 32s and would do 75 @ about 4300, but that was an OHC 4banger, horse of another color.
4. 5.13 seems like an odd ratio that may not be sitting on the shelf at your local 4X store if you need one in a pinch, especially if it's a D30 Reverse Rotation...4.88 is pretty common.
Anyway, the 4.88s will be a big improvement over stock and the 33s are a long way off, if they happen at all.
