Thanks to all who responded. The mounting studs are 5/16-24 thread. The original nuts were 7/16" across the flats even though standard 5/16-24 nuts are 1/2 inch across the flats.
I replaced one stud by cutting off a 5/16-24 allen cap screw. Installed it with threadlocker. Replaced the nuts with new nuts and split lockwashers.
I used an inspection
lamp, and 1/2" combination wrench to tighten the nuts. It took a few minutes to get used to the mirror image. I also put a loop of cord, cow hitched to the wrench, around my neck to keep it from falling into the bilge
I also replaced the fuel filter
with a Racor
500FG. After venting the fuel
system: bolt on top of paper fuel filter
(7/16" wrench), bolt on side of highpresure fuel pump
(5/16" wrench), bolt on side of speed governor (5/16" wrench), and high pressure nuts at injectors 3 and 4 (5/8" wrench), the engine
started and ran beautifully.