How do I get 5 bolt rear wheels

[resin addict]

Ok, bear with me because I'm relatively new to this, and I apoligize if this is a dumb question, but I've learned that the only dumb questions are the ones you don't ask; I have a '59 Apache stepside that I'm beginning to work on, my first project is having an I.F.S put on the front end. This will get me disc brakes, power steering and GM 5 bolt pattern for the wheels and tires, what I don't know is how do I get the same bolt pattern on the rear end?
Also, once this is done, what recomendations do you have for a new wheel and tire size. I want something that has a nice low profile, but I'm not really interested in going with way oversize rims with 2" of rubber exposed. I'd say the look i'm after is more of a late 60's early 70's muscle car look. Can I go with 8" rims on the back with 6" rims on the front to give me better handling?
Any advice will be greatly appreciated.
Thanks,
Randy