Regular machine screws are low strength. A stainless one could be used, or a hard cap screw etc., but even with a bottoming tap, there would be so few threads in there that there would not be much strength and the threads of the screw would be riding on the trunnion holes.
Replace it by welding on an appropriate sized universal joint used for driving socket tools. That may not have a long life though - but hell, give it a try.
Or-
If the hole is sized right cut the head and short amount of shank off 2 bolts (socket head [allen] bolts would be strong) that would be a very tight fit and press them in with a press. Also use some Loctite Bearing and Sleeve Retainer.