I have a1969 chevelle I bought that was under constuction.The car has a new built 454 at 500 hores the motor is very strong and built. the transmission is bad.I have a turbo 400 short shaft transmission out of a pickup that was a stong working trans,I will be putting it in place of bad trans in car now.I purchest a 12 bolt rear end but gearing are hight 2.71 I like the Idea of high gears but worry this will heat up trans or be hard on motor.I realy wanted a cruser car but the power is nice to .What gear would best work and what rpm rang would the moter run at on high way at 70 mile per. hour with 2.71,3.73,. I no the 10 bolt will not be strong enough so I need to put this 12 boit in its place any info would be great thanks. what rpm rang. 454 turbo 400 2.71 gears run at 70 mph = 454 turbo 400 3.73 gears run at 70 mph = 454 turbo 400 4.11 gears run at 70 mph = 454 turbo 400 4.56 gears run at 70 mph =