4.10 X .67 =2.75 final drive. Assuming stock rear tire size (26.6"), 336/26.6 X 2.75 X 70 = 2431 RPM in lock up.
Nice - I'm pretty sold on the idea of a 200-4R w/4.10 or 4.33's. Hey, I got it right! A 350 will live forever around 2500 RPM and even a mildly built 350 would be pretty darn quick with 4.10's.
The thing to do seemingly would be to dyno an engine first and start looking at trap RPM in 3rd. I certainly wouldn't be opposed to 4.56 if it'd be quicker. For a strictly street build it'd probably be the way to go.
4.30 rear gears with a 200-4R's lower 2.74 1st gear is the equivalent of a turbo 350 with 4.68 gears. 4.56 RGR w/200-4R is equivalent to 4.96. I had 5.13 gears in my street car with a turbo 400 for a few weeks. Nothing could beat me between stoplights because I could not spin a tire. It shifted into second gear at 6,000 RPM at a little more than a car length. Top speed was 90 MPH at 6,000 RPM with 30" tall tires. It took a long time to get anywhere without overdrive in those days.
Your point is exactly what I was trying to make in dynoing an engine 1st then picking the gear to optimize trap rpm. W/5.13's you'd run out of engine before the ¼ mile (might be perfect for ⅛ mi. track) but with 4.10's might be leaving something on the table at the top end. The OD trans gives you luxury of dialing that in on a car that you still want to drive on the highway. I'm sold on the idea - Now to just get that car to the point of needing a drive train. Unfortunately it's a ways off.
It was pretty amazing. That was with a pretty healthy 455 w/KB cheater cam and a KB switch pitch turbo 400. It would boil the tires at the second gear shift if you stayed in it and it barked third hard, like filling-loosing hard. I could spit the cassette out of the tape deck into the back seat. At college, a fellow student said my car wasn't that fast. He bet me he could outrun any car to 50ft. Not one to shy away from proving someone else wrong, I went home that weekend, replaced the 3.31s (12-bolt at the time) with a borrowed set of 5.13s and headed back to school. It normally takes about 50-60 minutes to make the trip. It took 90 with 5.13s because I couldn't stand it taking 4000 at 60MPH for the whole trip. Got the same gas mileage oddly enough, 12MPG. I let him take off when we wanted. I caught him and passed him by a fender at the 50ft mark. He couldn't believe it. Later he admitted everyone else he'd ever bet went up in smoke on the start. LOL A man's got to know his limitations.
Depending on their condition they'll most likely be for sale. I don't remember what brand they were but the shop that built the rear said the brand was notorious for having a "whine" and they were right they certainly did. Nothing horrible but you knew they were there! I'll know more in a month or so.
So a couple of you have suggested a 4.10 gear, will they bolt to the carrier in my ‘72 8.5 10 bolt that currently has 3.23 gears? Any brands preferred?
It should, carrier breaks for the GM 8.5 are 2.56 and down, and 2.73 and up. I have Yukon gears in mine. https://www.summitracing.com/parts/yga-10408
You may not have a choice if you want 4.10 gears. According to what I read, your carrier takes 2.73 and up gears. Oh, and Johnno did all his burnouts through the brakes. That's why he went through rears. Get a line lock.
