I am getting bumping and rattling noises from the back end. I was told my a friend that sub frame connectors would fix this problem. Is this true? Please help me out.

 

It won't completely get rid of them. It should minimize the noises though. It's better to get them before the chassis flex develops--but since you bought the cars with miles, you don't really have that option.

Also, the reason you find your T-tops difficult to lock in place is probably due chassis flex as well. If you have it bad enough, they won't even align properly and you'll develop leaks when it rains.

Edit: Take the "a" out of "metallic" in your sig.

 

Chassis flex occurs when the engine puts out so much torque it twists the cars frame. Your V6 will never, ever do that. Car with t-tops, sun-roof, verts are all less stable than a hardtop. Subframes will not get rid of noise. They will however make your car handle better. BMR is the best. I bought a package from them with a shock tower brace, panhard rod, and subframes for around $350. Great mod to have. I've found that sound that comes from my car has to do with the rubber gromets that are in place with the muffler, and pipe. The gromet right before the cat-converter was making these odd sounds, but I braced it so it stoped that sound. The two rubber gromets that support muffler can break aswell. My passenger side one did. Subframes ae great, but check these things first before you spend any money.