Rear Crossmember/Spring Slider/Spring Relocater

I still have a couple of things I need to figure out before I can put a price on it. A major one is how consistent are the widths of A-body frame rails? I also need to come up with a simple front spring mount. I have a few ideas but not everyone has a welder in there shop or the know how. I should have something figured out in the next week or so. I'll keep yall posted.