Suburban Squeak

[Templarum]

Hey!

I have an 89 Burb 1/2 ton with dual doors in the back. Normally little noises don't bother me, but there is a horribly loud squeak that comes from the rear whenever I'm moving. If I push down on the floor by the rear doors I can make the noise happen, just not as loud as when it's being driven.

The only obvious things I can see wrong are a rusty cross-brace running laterally behind the gas tank that the sill plate bolts to, and a wornout body mount. The brace is flaking badly, and I'd like to change it, but I can't find one for sale anywhere or even a good description of it in any manual.

Do any of you guys have experience with these cross-braces and too much noise? Any help or advice would be most appreciated.

Thanks,
David