i thought that the original 3 hole used the 3 "inside" holes that the standard 5 hole fender used... i suppose i could be wrong, but back in the late 80s when my bass instructor added one to his '74 precision he said that he didn't have to do anything but take the original off... just a thought.
fwiw my '75 RI looks like swiss cheese under the bridge thanks to the previous owner breaking off screw after screw in 3 positions where he had the original bridge installed. ugh, thats food for another thread tho
__________________ Artist | Musician | Bass Player
Life is what happens to you while you're busy making other plans. (o.o)