3.73's will not kill your top end to badly. 3.73's and 30 inch tires for me was 3000 rpm at 65-70 I had a 292/sm420. An OD trans which I'm putting in with my new 292 will give me about 2500 rpm at 70 mph which will be perfect. Your 230 is a smaller engine, though yes indeed it has great power and luckly plenty of torque at the lower range...you'd be making ANY engine struggle to be in 1:1 with 3.07's pulling grades. Heck, I get another axle from a 66 with 3.73's....swap it out...drive it and see how you like it...and if you don't...simply swap your old axle back in. I've done it and it takes very little time.
