Road Runner:
I'll try to post an updated picture, but for now you can just imagine it about 3/4" lower than my prior picture of the front half of the car, and yes it does have more space in front and back of the tire.
I ordered 17x9.5" rears with 4.5" backspace. As I mentioned, I have 5-3/8" from the rear drum mounting surface to the closest spot of the leafspring, so 4.5" backspace should barely work for me. If it rubs slightly or comes close to it, I can add a 1/8" spacer to push it out a little, and still have at least 1/2" of thread on the studs. Worst case I can relocate the springs, which I dont want to do, or I can install longer studs and use a slightly bigger spacer. It should be very tight but I expect at least about 3/8" from the inside of the tire to the spring.
If its a 2 piece wheel design it can usually be custom ordered, and yes it is more expensive, by about $70 per wheel in my case I think, and it takes an extra 6-8 weeks for delivery. Thats why I'm still waiting for the rears, and I got the fronts in 2 days.
Depending on the size of the tire, I think all stock rears can handle 4" backspace, and some cars can handle up to 5".
Your mileage may vary.