What frames will work on a 69 convertible frame? Will any hardtop frames work?

No, hardtop frames wont work because of the design of the two frames. The convert frame is boxed from the front of the frame to past the rear axle and the hardtop frame is an open channel frame between the front and rear axle areas, like this C as opposed to this D of a convert frame. Not a really accurate pic, but you get the idea/

You can take a regular hardtop frame and box it however. You can find an El Camino frame, and put the boxed parts from it to a hardtop frame and then you'll have a convertible frame. Its actually a little harder than how I made it sound, but yeah.

Convert frames are getting really expensive. I found one in Oklahoma for $1100 plus $400 shipping to Cali. I also found one in Arizona and they wanted $2400.

You can buy a hard top frame for 150-200 and an Elky frame for 150-200 and combine them. You'll make out a lot cheaper.

do you know what year and make of car frames will work if I decide to do it that way?

68-72 all work. There may be a few slight differences with them, but they all work from what I've heard and read on these forums.

Don't forget, convertible bodies (and frames) have an extra pair of body mounts under the front cowl area.