I was looking through all the companies to find the toughest subframe connectors on the market and what i found (and heard was the strongest) was the Western Motorsports full length subframe connectors. I think the site is
www.wmsracing.com . It's made out of very thick gauge roll bar tubing and is a weld on design that connects the front subframe, rear subframe and torque box on each side. Very tough looking. They also advertise in Muscle Mustangs and Fast Fords magazine, but they usually show their engine management system and air intake. The packaging sucked and there weren't any directions, but the product speaks for itself in it's quality. I'd be happier if it showed exactly how to weld it in, but it should be easy to figure it out. Other than that, Kenny brown has good full length subframe connectors, and also a brace kit called the extreme matrix brace which looks like it'd really stiffen up anything. Any weld in full length subframe connectors should really be enough, just some ideas. Good luck.
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'84 Mustang 5.0 LX
My car