20" Detroit Steelies on a '71 static 3-5 drop

[AZBuckHunter]

I've been researching and appreciate all the info already out there.
I'm about ready to order some Detroit D-Town Smoothie's

Looking for input on my selection below as well as tire size option for rear. Do I need to be worried about their rim width being 1" wider for the lip to lip measurement? (see image)

I have a 71 swb, orig rear end, adjustable trac bar, 3/5 static drop, factory bed no tub

Front
Wheels – 20x8
Backspace – 4.75
Tires – 245-45-20 or 245-65-20

Rear
Wheels – 20x9 or 20x11
Backspace – 5” or 7”
Tires - ?

Detroit's size and backspacing image attached.

Thank you