At wits end!

When you set the timing, make sure no vacuum is going to the distributor. I'd pull & plug the line to make sure.

While you can use more timing then 6/7 BTDC, a stock teen should still not do what your describing even at that setting. It really sounds like a lean issue......Like was mentioned above, even though you did the rebuild, it still sounds like a low float setting, accelerator pump issue, or a vacuum leak.