Trying to install Win7 from a universal x86/x64 disc with Bootcamp 5

I'm on a 27" iMac late 2012 iMac13,2 Mountain Lion... latest version.

I know that Bootcamp 5 only works with Windows 7/8 x64, however I only have an install disc with both x86 & x64 Ultimate 7 on it. I tried using Bootcamp 4 but am having no such luck.

I've tried editing the Info.plist in Bootcamp, but am not really sure if there's a line I can add, alter, or delete.

I'm wondering if there's anything I can do to either:

1: Make Bootcamp work with my disc, or

2: Alter my disc to make it only x64.

Also, the "Install Windows 7" option is greyed out, but I'm currently operating on the notion that this is probably due to the computer not seeing a supported install disc.

Any help would be appreciated!