Sorry to resurrect this thread with more ignorant questions.
I'm not going to re-drill and tap, so I'm sticking with my new rails and the #6-48 screws, and I'm hoping to finish this project and "permanently" attach the rail to reduce movement of this component.
Question - what type of JB Weld is strong enough to work for these purposes, especially in the off-chance I change my mind down the road? It looks like the original can withstand 5020 PSI and 550 degrees and I expect would be the hardest to remove. It looks like KwikWeld withstands 3127 PSI and 300 degrees (so I'm guessing easier to remove down the road) and sets up faster. Would that be sufficient?