what pulley sizes?

i plan on taking my tractor off-roading, road riding, hillclimbing, mudding, and something i can just have fun on. I have a couple questions on it. 1.) What is a good speed for it? 2.) What sizes of pulleys should i use for that speed? 3.) For that speed are there any further mods that i can do to help the thing hold together longer or make it safer?

To make my trans axle hold up for longer i put grease nipples in a few places in between the input needle bearings and on the top of the trans axle so i can add grease more frequently, easier. Also make sure all the bolts are tightened evenly all the way around the trans axle to keep the case from cracking. I have like a 4 inch front pulley and a 5 inch rear or something close to that and it goes about 15 miles per hour.

A 1 to 1 pulley ratio is pretty popular just guesing you would git about 15mph. You may want to upgrade the brakes and steering . And X2 on the grease fittings for the trans its alot better to just pump in some grease with a grease gun then take it apart to lube it , I would recomend a rubber cap on the fitting to keep water out .

Reinforce the body first off. 1x1 square tube steel will do it.

Clean up your steering so you have less or no slop at all.

A 1:1 ratio is really what you want if you plan on offroading. Unfortunately you cant have both road speed and offroad traction with a belt setup.