I'm looking to replace my stock 20's with some aftermarket 20's. They are 20x9 with 5 3/4 backspacing and +18mm of offset. How does this compare with the stock wheel? Will these stick out more or be the same as stock?

 

hey buddy, first post!!!
That fitment is correct for you sir. It should sit flush with the fender (looking at the car front to back)
IMO, as long as the car isn't lowered pass an 1 1/2, a 255/45/20 is the best fitment for it.

What kind of wheel is it?

 

They're going on an 04' Quad Cab 2wd, so I'm think of putting some 305/50R20's on'em. I'm debating between two wheels, both by Ultra. Either the type 140 Stargazer ot the type 243 Mako. Not sure yet.
http://www.ultrawheel.com/wheel_deta...d=1&id=145
http://www.ultrawheel.com/wheel_deta...d=1&id=128

 

lol, nevermind on the tire size than

 

I'd say the first wheel is what i like better (#243). 305/50/20 is good fitment on the truck.