Options for replacement lathe spindle motor

...though replacing the BLDC motor on the mill with a servo was precisely because it fitted the same highly restricted space envelope, for the same power, for less than the price of the replacement BLDC control board which I'd blown twice (okay, factor in the new pulley and belt and it was probably a bit more total cost), but it removed all the analogue uncertainty of spindle speed control or any third-party interfaces (that spindle, also step/dir control). Plus (and some might cringe at this) - the option of a spindle lock

Servos have very good speed control. AC servos pack a huge amount of power into their small size.

Downsides of servos
Need some tuning - pretty easy with a decent brand
Cost - may or may not be more than a non servo setup depending on brands and a bunch of factors.

Hey there, how did you get on with the AC servo spindle on the myford?
I am considering it on a BUD Boxford conversion.

It's fine - I've no problem with the servo as a solution. It did require, of course, a special-to-type cradle to mount it on the ML7 but nothing that 10 minutes with a TIG, and 20 minutes with a grinder can't fix.