Another backspacing question

[BlackBetty83]

Hey guys I know this is probably repeated but, I have looked through the forum and have noticed that in the rear a 15X10 is best used with a 5 inch backspacing but I am finding it difficult to find wheels I want on my truck with that much backspacing.
I have how ever found many 15X10 with a 4 inch backspacing pretty easily. are theses even an option for me or is 4 inch just shy of the clearance I need.
I have seen some of you guys running 4.25 backspacing as well do you guys have any fitmitent issues??

Also if I want to run a 15X8 in the front what backspacing is best with my drop? I am going to assume 4-5 inches is ok?
I can find some really expensive 15X10 with 5 inch BS but they don't sell the matching fronts wheels.
Thanks so much for your time!

A set fo wheels I am looking at =http://www.wheelsforless.com/detail.aspx?ID=6568

Truck is a 83 Chevy C-10 Fleetside with a 12 bolt rear end and I plan on a 5/6 flip kit drop.