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Got several motors and gear boxes at the sale and MIGHT have a couple for both sb lathes. pix later of them.

make sure your lathes are solidly grounded Sonny..old motors are notorious for insulation failures,don't become part of that circuit my friend

The auction motors are new style modern motors. The one on the 10 foot SB is the antique jobber.
I even got a couple 3-phase motors to try making a rotary converter with.
One of the single phase ones is 2 hp and the shaft is close size of the old motor so now I can figure out how to fit the drive sprocket to it and still use the chain drive.
Rpm's might be different so not sure about if that will hurt anything or not.
Mostly it's a try and see thingy! lol!
Ay least it's more than I had!

Sonny when you go to make your rotary phase converter, use black start capacitors rated 370V, and the silver run capacitors at 440V or better..this will make it last longer as the caps aren't stressed running at max voltage..
The formula I used was 100MFD per idler motor HP on the start side and 10MFD per HP on the run side..the run side runs the 3-phase idler all the time and the start caps cut in only when starting the idler then disconnect once the voltage setpoint is reached or times out with a timing relay, depends on how you build it. There's a lot of tuning that can be done to balance the voltages depending on load applied.
I used to use a SquareD voltage sense relay to cut the start cap contactor out once it reached voltage..it worked good but is no longer available..there are 'Potential relays" out there made by 'Mars' that work great.

My rotary was put together back in 1993 and is still running strong. I used 50amp contactors thruout. For the start contactor use a 3-pole contactor and wire all poles in parallel..it makes for one big start relay.
I get my capacitors from Surplus City Liquidators in Lebanon,IN..good people with a great website easy to use ordering..
they have contactors as well at great prices as compared to buying new.-Its all new, just surplus..nothing wrong with it.
Surplus City Liquidators

Sounds like you got this figured out!! I checked the link and their prices are great!
Now to find the ones with the right specs!

Sonny Ive built a lot of 'em,used to do it as a sideline..anyway a 1725/1750rpm motor is easier and faster to accelerate than a 3450rpm motor..they run quieter and the bearings last longer..use a 30 or 50amp dryer cord with a receptacle on the wall then you don't need a disconnect for the converter..I usually use a 12x12x6"deep junction box and mount it right to the side of the motor; take the small motor terminal lead box off, then bolt the bigger box right to the motor where the small box was..put all your relays and capacitors in it,keeps wiring shorter and gives you knockouts in the top and sides.

I think the motors I bought are 1725, 1740 range. Gotta get pix. of the tags. Have a lot going on so it will be a couple days!

this is one of the 3 phase jobbers

yep the 2HP Baldor looks like a good candidate

wonder if I could unbolt the gear stuff off this one and just have the motor? Dont need all the gear stuff hangin on it for and idler if this is the one I end up using.

take the green gearbox apart, likely the gearbox has a gear thats keyed to the motor shaft and has a locknut on the end..it's a special shaft motor..part of the gearbox thats bolts to the motor will probably support the end of the shaft with a bearing.You'll need to retain that so be careful where you cut the shaft off at.