Quote from Rog:
" but if it is stock, someone took alot of time to buff out where the mounting ears were....Rog"

Thank you, Rog for noticing what drew me into this. When I saw the bolts, I figured more than two of the mounting lugs had broken and some enterprising individual that still wanted the use of his trusty Pee Wee! When I looked for this evidence, I could not find it!
It looks as though the backplate were cast without any mounting lugs.

Yes I suspect there are round head screw heads inside the tank. The most notable feature of this engine is of course those two (obviously intended for mounting) studs sticking out of the backplate. As noted already, these most likely are not actual studs but just regular machine screws with the heads of the screws in the tank.
My surprise in this engine is the fact I am unable to see any evidence of the original mounting lugs. As Rog pointed out someone must have worked hard to make the backplate look nice after the lugs were gone. Surely all four lugs could not have departed the backplate so cleanly?

Most likely this backplate has been modified. If not, I wonder about the intent for usage!

Robert