What's the rest of the truck look like? Worth pulling the engine to freshen it up w/ gaskets, seals, and fix that bolt? You could remove the timing cover and repeat the procedure, and you'd probably have good luck with that. Remove timing cover, weld nut onto remaining stud, remove bolt. The probability of that working is actually greater than 50%, so it's worth considering. Could put a timing chain in while you're at it.

If all the other bolts are removed, you could put it back together with some rtv and skip that bolt. I've done that plenty in the past also....but the next stage is to struggle is to get the bolt out in place or pull the engine and use the proper tools with accessibility.

SBF water pump bolts are like the final boss in a video game.