72 C15 Centerline Tomahawk Smoothie question

[MalibuMulisha]

Hi everybody, long time reader, first time poster here. Quick question...

My truck is a 72 c15 with a 4-6 drop waiting to be installed, I want to use the tomahawk smoothie wheels in a 20"x 8.5. The two available backspacing options are 5.4" and 6" backspacing...with the 4-6 drop which backspacing is recommended as I dont have tires yet and work in the industry so potential sizing isnt an issue. Any help would be very much appreciated


here is a pic of my current set up