any type of silicone will not work! even if impervious to oil/gas.
IF you must use this type of sealant I would opt for 1211 by DOW...
Alex, what I have done with several different types of conditions regarding water, oil, gas, and gear lube in the past.
drain the case so there is no oil weeping into threads. take a box rag (white or similar) and soak with brakleen or acetone and thoroughly clean the threaded holes. If you choose to use brakleen and spray directly into the hole with short burst, be sure it all has evaporated so as to not contaminate any new gear lube.
find the thread/pitch size and order these:
if the thread depth is 3/4, then order 1/2 length, if the thread depth is 1", then order 3/4, and so on...
McMaster-Carr
preferably stainless 18-8 is fine.
side note: I have also used aluminum allen socket head pipe plugs in this manner...
clean the set screw/bolt with brakleen or acetone.
Mix up some 2 part epoxy, JB weld is great for this. either one will work, the KWIK WELD or the longer cure time JB will do the job, depending on your desire and location of the bolts.
wipe the set screws/bolts evenly with the JB weld on the threads uniformly, thread into the holes until flush, wipe off any excess epoxy, your done...
IF you EVER NEED to get these out, HIGH heat/torch will break the bond.
This is what I would do if it were my rig...
Good luck buddy!
of course after 24 hours, refill the TC...
***you can see if the far lower right hand corner the RED 1/8 NPT plugs set in JB weld in this exhaust stinger which has exhaust heat and water flow... and those are good until they can be removed, basically for the life of the part... just an example... Buddy!
This is what 1211 is used for: