Backspacing on 20x8.5?

I'm looking at getting some 20's soon hopefully, but I'm not sure what backspacing to get. The rims are 20x8.5. The truck is bagged, and will be body dropped at some point. Oh yeah, it's a 93 Dakota. Thanks

I got some 20x8.5" boyds this summer and they tuck. They have a backspacing of 6.75" which is the biggest they said they would make. Not sure about a 93 tho.