Right now we got a 28 tire going 135 mph, but turning 7400-7500 through the traps. Would like to be at 7000, and the math says a 4.30. I'm thinking real world might not be 500 rpm, so considering 4.10. Thoughts? Also in back of my mind is a 4.30 gear set has 43 teeth, so stuffing an extra 2 teeth would result in a weaker gear set, car has a 1.30-1.34 60'.

My math (Moroso dream wheel) using 7500 w/4.56 says 7100 with 4.30 and 6750 with 4.10. Peak torque RPM, etc., might change those numbers some.

Usually, putting in taller gears results in a little extra converter slip, so you don’t always get the reduction in trap rpm the math would indicate.

How much converter slippages does your math show now?
I swap gears on my old pump gas Duster from 3.73 ,3.91,4.10 and 4.30 and saw no real differences in the 1/4 mile performances
It did spend a lot longer in high gear with the 3.73
I had the Mopar 2.77 low gear set in the 727 also
I also ran a set of 315x60x15 ET Street Radials and then a set of 10.5x31x15 W M/T drag slicks on ten inch wide rims on the slicks, those bigger tires wouldn't fit in my car on 12 inch wide rims. The circumference between the two was around 6.0 inches and the car would cross the finish line at 7000 RPM on the radials and 6500 RPM on the taller 10.5x31x15W bias ply slicks

I ran 28 in tire on my Duster
4.88 in the 1/8th Perfect!
4.56 in the quarter--Perfect! but I was turning about 350- RPM less than you so.......
I would not do the 4.10 route unless you plan on NOS then oh yea that will be perfect

Dream wheel indicates just a few hundred (if that) slippage in the lights. Converter must be really efficient. 60' is good for the MPH. Car should be in the 9s. Doesn't look like you're leaving a lot on the table.

Each ratio change is roughly 5%. Like Dwayne said converter may slip slightly more. At 7000 rpm 5% is 350 rpm less with the 4.30, 7150-7250, 6800-6900 with the 4.10. My bet is the 4.10 will get it due to a little added converter slip. Both the 4.10 and the 4.30 have 10 pinion teeth so no difference in strength.
Doug

I recently went from 4.56 to 4.10 with a 28. My car is slower, 124 MPH. In my case The motor was losing steam with the 4.56 and showing very little converter slip because of it. I changed a few things with the 4.10 setup, looser converter, and 727 to 904. The car picked up at every increment, execpt mph. My finish line RPM only changed 200 or so due to converter slip.

Car has been 9.70's, with a stock block and no oiling mods other than a 1/2" pick-up. I think I like the 4.10's better after reading your replies, just don't want to sacrifice ET too much. So a consensus would be no difference in durability issues between 4.10, or 4.30 gear sets?

I have with me in it, a 3200 lb 64 dodge NSS car. It also has the low gear set in transmission. Et and MPH are the same with 4:10 and 4:30 gears. On slick tracks it hooks a little more consistent with the 4:10 gears. 60 foot times are a little better with the 4:30's but if you average several time slips they are almost identical, at least in my car. run a 31 inch tall, 10.5 W slick.

I found very little difference between 4.10 and 4.30 in my current NSS car as well. I think it will actually MPH a little better with the 4.10. Once the suspension is right either one hooks without issue. 10.5wx31 std 2.45 1st, 3340lbs. 1.255, 1.258 60ft this weekend before it broke the ring gear. It's been 1.240 with the 4.10.
Doug