New guy with old problems...

I have a 73 nova, 406, glide, 4:56 12 bolt, solid motor mounts, rubber trans mount, slapper bars. I have broke 4 transmissions in this thing. It is only putting out about 550 horse. IT keeps breaking the trans in the case right around where the pump recess is and in the bell housing.

Has anyone had this problem before?

Swap your trans witha turbo 400, it's practically bullet proff. You can put way more 550 horse to it with no issues. This is your best bet and will save you tons of time nad money in the long run. I wouldn't recommend any other trans ever again. I went through aglide and 2 turbo 350's before going to the 400 and have never looked back.