Well, just got back into town this p.m. and have already partially drained the rad., removed the overflow bottle, removed the fan and shroud and the hole is very accessible.
Early this week I purchased parts/materials for several options for the fix:
1. D/T and use a heli-coil for the original 8mm bolt, or
2. D/T and use a 'threaded insert' for the original 8mm bolt, or
3. D/T for a 10mm x 1.5 bolt.

The heli-coil has very 'prissy' threads, but they are steel.
The threaded insert is a solid piece that is very beefy, but requires enlarging the hole to a 1/2", then tapping. I am considering the #2 option.
The 10mm bolt is just a tad larger than the hole in the CPS bracket, but could easily be drilled out for the larger bolt.
I really like the idea of going back with steel threads rather than continuing with the aluminum threads.

Will keep you posted on the final choice.