C4 trans 4:11 gears and 35 in tires. What great do I need?

We do not have a tire size and gear calculator for the Dana 20 gears. You will need to start somewhere, normally mid range if you have nothing to get a base speed. Or if you know how many teeth the gear is now, take that number, then adjust the number of teeth more or less, to get the speedometer to match as close as possible.