as long as your tires don't go above 32's regearing isn't that big of an issue if your not lifting that shouldn't be a problem.
a set of 265-70-17 or 265-75-16 should fill things out nicely and not rub as far as the armor goes it depends on what bumper you go with. if your planning on adding a winch and running steel rope add around 100# for a warn m8000 or 9000 series winches. if you go synthetic like viking or amsteel blueyou can shave off around 40 to 50 pounds of cable pretty drastic.
hers what i would suggest talk to eric he owns relentless go with his aluminum front bumper they are solid as hell he builds them right frame straps gussets galore and they are very light compared to plate steel. then go for a winch and synthetic rope that should give you the set-up you want but, keep the weight reasonable so you won't have to swap in new springs.
as far as acceleration goes lol it should not really effect anything if you go this route but, if you ever wanted a fast truck you should have bought the v6
theres something about the 4cyl toyota trucks i just dig though.
hope this helps