Hey Keith, how's it goin'?
Saw an article on that subframe kit in "Classic Trucks" magazine awhile ago-looks like a sturdy, well-built unit. Also looks easier to install than the factory subframe job.
As for your rear axle question, take a look at the "Tech Tips" section here at Stovebolt, I believe there is a listing of rear axle widths available. If you can't find it here, try the "Technical" section at chevytrucks.org-I'm quite sure they have it there.
Good luck with your project.
Regards,
Wannabe
