My book says that little gem goes 142 lbs (w E-start). The ’59 parts list says it uses a ‘standard’ mag, so I assume the ’58 does too. McC made a mid-year change to the mag in ’59, so ignition parts for the older motors may be uncommon ? It also shows the bail-o-matic, which wasn’t everybody’s cup of tea.
I don’t know that the engine itself was substantially different from its contemporaries – it seems Sears sold several of them until McC spit the bit.

I don’t like your chances of finding specifically a ’58, but I have actually been wrong once or thrice before.

My aftermarket service manual (covering ’58-’65) shows a picture of the cooling/bail pumps mounted on the lower unit. However, there’s an ominous (?) note that this is for ‘later’ models with the ‘earlier’ two-cylinders having the pumps in the lower motor housing. ‘later’ in this case starts with ’59.

It also says you can expect to find twin Carter model N carbs. Or Tillotsons. Or maybe even Walbros. Looks like McC used them all.

Some guys have all the luck, I tell ya….You just have cool all over the place, there. I mean, yeah, it should have a period correct engine to go with the dash; but a short shaft 75 Evinrude, too???? How often do you see THAT? That is a very desirable engine, to the right person.