Don't think you have told us what size truck you have yet?
If it's a 1.5 or 2 ton then 20" wheels are stock.
If it's a 1 ton then 17" single wheels, or 18" dual wheels are stock.
If it's a 1/2 ton then I can't think of a good reason to use 20" wheels, probably not even 18" wheels.
Take a look at trucks like yours, and like you want yours to look, if you can "preview" your ideas on someone else's truck it may help to decide what you want.
Grigg
