17" Wheel Users, Please

[RKHiPerformance]

I'm about to order a set of 17" wheels for my car. My plan is to use a 17X8" wheel in the front (4" BS, 245/45 tire)) and a 17X9.5" in the rear (4.75" BS, 275/40 tire).
I'm having difficulty confirming the backspacing. Both the Tire Rack and Boyd Coddington suggest a 5.25" BS for the rear wheel, but I've spoken to users with 9.5's in the rear and they are using the 4.75" BS. Autotrend also suggests the 4.75 - 4.85" BS. These sources say a 5.25" BS won't work.

Can anyone offer any insight? Are there any other resources I can turn to for a proven fitment combination?

I really appreciate any help.

 

[2QUIK6]

I'm cofused on the BS needed for 9.5" wide rims also. For all the diagrams I've seen, an increase in backspacing would bring the inside lip of the rip that much closer to the frame rails, but appearently that isn't true. Stock 7" wide GN rims have a 4" BS, but if you increase the rim by 2.5", and keep the same 4" BS, that WILL NOT push the outer lip out by 2.5" for some reason, and no one can seem to explain that how width changes with the same BS effects the inside distance of the rim lip to the frame rail.

 

[RKturbo6]

A friend of mine had 17" Budniks with 315/35/17 Nittos on his Chevelle and I wanted to order some so I tried his 17x9.5 with 5.50 BS and it was not even close to getting all the way on the studs without hitting the frame rail. I have spoken to couple of the other guys on here with them and all seem to get the 17x9.5 4.75 BS. I have aluminum drums (which one of the other guys did not) so I ordered mine with 4 7/8 BS. Also 315/35/17. After doing some measuring I think it will fit fine. Although it will be reeeaaalll close. GL