apex and forgestar wheel backspace help

[CamaroJesse]

Ive been on the hunt for a quality but affordable wheel. I may have narrowed it down between apex wheels or forgestars.

http://www.apexraceparts.com/apex-pr.../#.VV-s8flVhBc

http://www.forgestar.com/v2/wheelsf14.php


I have seen a few 1st gen f bodys with these wheels on them but i cant find info about backspace or rear end widths. This is for a 67 firebird. Im in the process of buying a new rear end and im wondering if i should go with stock camaro or firebird length or even go wider? Im wondering because of the lack of dish on these types of wheels. I do not want to run adapters. So im just trying to figure out a good rear end length to go with to make sure that these wheels will fit with the available offset without adapters.

thanks!