Master Brake Cylinder

I recently purchased a TRW Master Brake cylinder for my 1997 740i. The box has the cor=rect BMW part number 31316764190 . I matched it up with the unit in the can and it appears to be the same. The only difference is that the old unit has only one threaded entry for a brake line in the horizontal body of the unit and the new one has two. one opposite the other, on the old unit the opposite hole is molded sealed. I am thinking that I can just apply threadblocker to the unused plug nut that came with the new unit and close off the unused input. The question is will brake fluid dissolve the threadblocker?

Not if you use the correct grade. Check with Loctite and see what they recommend.