Look here....
I feel that most of the broken mounting studs and mounting areas are due to improper mounting. You can not put these studs/mounts in a bind and expect not to break something. The material these engines are made with are probably the lowest grade that will basically stay together under almost ideal conditions.
I made this bracket. I took a piece of angle iron, drilled the two mounting holes and mounted it to the front of the engine. Then I attached the back mount.. I left just enough clearance to slide the engine down until the angle iron met the front tube. Marked where both met the rear mount and the angle iron rested on the front tube, removed the angle iron mount and wielded the brace that the muffler clamp, clamps to the frame. NO mounting studs/nuts are torqued over 50 inch pounds (3-5 foot pounds), and double nutted with lock nuts...except the muffler clamp. I also made a bracket to keep the engine from rotating on the frame when torque is applied during running.
The third picture is why you DON'T DRILL HOLES. That frame tube is split in two. I since then repaired the frame.