3.75 is ideal. you will be fine with 3.5
why are you putting so much money into outside mods, with stock suspension? ya know that front glass is $500 to get here alone, plus painting?
if you not already a member, join up on the Ontario ranger club facebook page. we can help yu ut with building the truck of your dreams, and show you what works, what doesnt, and whats the best to save money.
BTW, take those tires back, tell the supplier his a dumbass and demand your money back.