Since you will be pullied, I'd say it's a choice between 3.73 and 3.90. 3.73 will make a small difference. I really don't know if it's worth it. Maybe yes, maybe no. 3.90 will multiply your torque by about 10%. In other words, you would feel like you had 10% higher torque numbers. The only problem would be can you get traction with the 3.90. I don't know the answer to that. Maybe you can find a guy with a pulley and 3.90 and see what he thinks. 4.10 would be too much in my opinion. When I eventually pulley, I will probably have to switch gears again.