Options to stiffen chassis 69 Firebird?

[Nativefx]

Originally Posted by Build-It-Break-it

"My question is, what are some of my options to help stiffen the chassis?
Because I finally decided Air Ride was a must and not knowing of any aftermarket options that was designed to use Shockwaves at the time, I decided to use my stock subframe and already had it modified, sandblasted & powdercoated"

I think he already modified his front factory subframe and is trying to find ways to stiffen everything from there.

Yes, I have already purchased the Air Ride, Baer Brakes, and 9" rear end with the Baer floater system so I may be to far to really consider a full frame. If it would have been an option when i started buying all of this, it might have been a strong consideration. I'm just looking for options to would improve what I have, and the Alston sub connector might take some research. I will have the exhaust custom made later on so that won't be an issue.