A 7" wheel with 0 offset has exactly 4" backspacing. Not enough offset to work on most A bodies. Like Abodyjoe says, a 4.50" backspacing 7" wheel works well with most reasonably sized tires, like a 225. On a 7" wheel 4.50" backspacing is equal to +1/2" or +13mm offset. If you want to run a 1" thick spacer you'll need 1" more backspacing or 1" more positive offset, which means 5" backspacing or +38 offset on a 7" wheel.
Your option of going to the wider 8" wheel solves nothing, except that most likely won't fit on the car at all. The 8" wheel with 4.50" backspacing you mention is still a 0 offset wheel.