I was able to clean the area around the boss pretty well this morning after draining the trans fluid. Test fit the parts, took a deep breath and mixed up the JB Weld then applied a layer to the inside of the machined cap. Stuck the cap on the boss then inserted the pipe plug with washers and snugged it up to force the epoxy around the perimeter of the boss and hopefully into the crack. I used quick setting epoxy so after about 15 minutes, I removed the pipe plug and inspected the repair. It looks like a half turn with a 1/8" pipe tap loaded up with heavy grease to trap any shavings will clean out the small amount of goop left in the threads. I'm cautiously optimistic.
Meanwhile, I machined an o-ring groove in the end of the plug that came out of the port. I'm hoping a 009 o-ring will seal down in the bore below the threads. Taken together, perhaps the two fixes will stop the leak. Should know more tomorrow.
With the repair job under my belt, I returned to the front bumper adjustments. A few shims and gradual tightening of the mounting bolts has it fitting pretty nicely. Once that was done, I installed the headlights to top it all off. Still have a few things on my punch list, but I'm getting closer all the time. If the tranny deal works out, I'll only have lost a day or two. If not, I'll likely be down for a week or two. But since I'm on retirement hours it doesn't really matter.