Any tail housing will work when properly set-up. Look at a 727 compared to other transmisions. The tail is very long. There's not any support way out at the end. When the drive shaft fits correctly,the pinion angle doesn't pull over center at launch, and the shaft is balanced with tight u-joints there won't be a problem. The only other cause is chassis flex. The stock crossmember and mount don't seem to be an issue. Unless the car has no frame connectors or cage and it is in the power range that it should have them. Tube chassis could be a different issue as I have no experiance with them. If I had a car with a tube chassis and it flexed more than a stocker I'd be worried about more than trans cracking.
Doug