wheel size
Oh boy! Put your flame suit on. 
Now to answer your question
yes 20x8.5s will work. I think depending on what size tire (I would think 255/35-20 would work well) 4" - 4.25" backspace should be good.
Product ID: F11721061 Finish: Chrome Plated Wheels
Product Name: Nitrous 5 20x10 5/4.75 rear
Description: Foose Nitrous 5 one-piece chrome plated custom wheels from the drawing board of Chip Foose. -6mm Offset, 5.25" Backspace
Product ID: F11728561 Finish: Chrome Plated Wheels
Product Name: Nitrous 5 20x8.5 5/4.75 front
Description: Foose Nitrous 5 one-piece chrome plated custom wheels from the drawing board of Chip Foose. -6mm Offset, 4.5" Backspace
will these look right on my car (1981) i want the wheel edge even with the wheel wells










