'65 ca77 petcock rebuild....can-O- Worms !

I've seen worse in some pics, and I understand these can be troublesome, but I'm giving it a shot. Bought the kit. When taking it apart, I found Two out of three of the screws appear to be the oddball m5 X .9 pitch X 25 JIS. But the third screw is a "regular" metric 5mm X .8 pitch. Luckily, they didn't screw up the threads in the tank with it because it was a shorter screw. Now some folks just drill and tap for something more regular, but I'm going to try to get one of those stock screws. Just talking out loud here.....