[cableguy0]

I would save the cash and build a th350 or th400. The only overdrive worth bothering with if your making any real power is a 4l80e. The 700r4 is a weak unit. You can dump a ton of cash into them and still end up with a trashed unit. They will not live in a heavy truck with a bunch of power. Its that simple. The overdrive clutches especially are weak due to there size. They are tiny. If you burned the 3-4 clutches its likely the converter has entirely too much trash in it to stick it in another unit. I wouldnt risk it. It doesnt take much debris to make a valve stick or tear up the friction surfaces. If I were in your shoes I would go to the junkyard and grab a 4l80 core. Buy a decent converter. Get an upgraded sprag and have it rebuilt. It will hold your power level with 0 issues for a very long time. The only issue is making it work. You can buy a standalone electronic controller or convert it to a full manual valve body. You can either buy a complete valve body or buy the trans-go conversion kit. The trans-go kit is the cheapest option.