Depending on the rules, will determine what you can do...
That aside, dont use bolt-in ANYTHING! Bolts allow for minor shifting between the bolt and the hole. THAT is the part you are trying to eliminate.
Get WELDED subframes first. Then, if you really think you need it, go to a welded cage. IMOHO, unless you are seriously upgrading your suspension and sticky tires, the weight of the cage and the little difference it will make, aint worth the weight.
As for companies, MM is all out good for a street car. I have been impressed with people I know that have their equipment. If you wanna spend some serious bucks, then I would call Griggs.
Try to stick with one company. You start getting mis-matched parts mixing pieces from different companies.
------------------
Darius Rudis
Roadracer: Home built t-arm/panhard suspension powered by an S-trimmed motor :-)
My Mustang Page