71' dart 28" x 9" Slicks

I have a 71' dart Mancini offset shackles
15" x 8" wheel with 28"x 9" M/T ET slicks
I have 4.75" back spacing wheels.
Not enough b.p.
Measuring looks like a 5.5" b.p. Would clear
Anyone running a similar set up could shed some light.
Going to be a tight fit.
Thanks