I can't remember what size those screws are. Jon (carbking) probably knows. You could use J.B. Weld to hold a slightly smaller screw in the hole and then use a nut on it. Heli-Coil does make a 10-32 size. There is also a product known as Thread-Restorer (think Loctite makes it). I've had luck with that if the screw doesn't need to be too tight. What year and size of engine?

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end