I was wondering if there was any other gears I can put into my D40 rear end.
Currently it has a 2:1 ratio
My problem is since I no longer have the original running gear I wanted to run a L6 250 motor and th350 tranny, but most of the calculators are showing I will have far to much top end speed and the motor will run between 700-1500 rpm. Great for fuel comsuption but hard at low speeds?

I really wat to stick with the wooden wheels so changing out the rear end for a modern set up is not much of an option, unless I go full custom which will change the look of teh car completely

Do You own a car built by Durant? D40

You've made some mistake in your calculation. The ratio is more like 4.00 to 1. Are you sure you have enough distance between the cowl and radiator for a straight six chevy? A Chevy Nova 4 cyl would be more like it. Or approximately 1994 Dodge Dakota 4 cyl (Jeep-built). I don't think it would be a big challenge to find a more modern rear axle and have it modified to use wooden wheels. Hot rodders change the spring mounts and tread width all the time.

Do You own a car built by Durant? yes