Hi .
I have a '70 454 chevelle with a m-22. I currently have 4:10 in the rear and the car is useless on the highway. I will be running a 27"tire in the back. Should I go to 3.31 or 3.73? I need to use the highway to go anywhere, but I still want the car to be a screamer. Does anyone have a similar combination have any advice?

3.55's or 3.42's would be a good compromise. If you changed to wide ratio gears in the tranny 3.07's would make for even better hwy cruising.

3.31 will give you around 2900 rpm at 70 mph. 3.73 will be about 3200 With the Big Blocks torque you would probably be ok with the 3.31's I have 3.73's in my Heavy Chevy and also had them in a 73 Z-28 and I loved them but they are both small block cars.

Either way will be a compromise and it will not be a "screamer" with the 3.31's, at least not until it gets moving.

3.42 and 27" tall tires is a nice combo

How much of a screamer is the motor? I have a 2.73 in mine, and it screams everywhere, but I have 650 hp too.

Yeah LOL 650hp and a 2.73 would be nice. Mine however is around 400, with a 2.73 rear end my daily driver honda would probably keep up to it in a 1/4 mile.

A wide ratio transmission makes no difference when you are in 4th gear. 1st,2nd,and 3rd gears can be different in different transmissions but, 4th gear is 1 to 1 no matter which trans. Might consider a T-5, which has overdrive.