First, you don't need 2 strong bolt over there, one strong one and one ok
are fair enough, can you manage to drill this one right? can you tap this
one? you just need an helicoil over there so the bold hold ok.... put some
518 locktite and drive the van....

Or drill and remove the rest of the screw, put some JB Weld inside and drill
/ tap the hole, that should be enough for years to come (i did the same
mistake on my 84).

Of course, removing the head to work on this one would be best, but be ready
for some $$$$$$....

Cheers