Looking to find an OE 1973427 for the original 1111973 69 H/O distributor. I checked it and the diaphragm's toast. Pretty sure it's the original as it's numbered "427". I know, it's probably as easy to find as the 973 itself.

Not sure what the service replacement distributor 989 used. Probably the same.

 

Is the vacuum nipple straight,or a curved 90*. That might narrow it down some.

 

It's a 90. See the pics here.