I turn on an old Oliver 20-C Patternmaker's Lathe and wouldn't trade
it for any other on the market. I can turn 24" in diameter and almost
8' long inboard and from spindle to floor/ceiling outboard. It has a
4 step flat belt pully drive system run by a 5HP motor with 4 speed
gear box. The spindle is threaded 1-7/8" x 6 tpi with #4 Morse Tapers
in head and tailstocks.

You can buy MT adaptors inexpensively from Enco, MSC or on Ebay. For
~$100 I had an adaptor turned by a machinist to allow use of my 1-1/4"
x 8 tpi faceplates and chucks.

The only changes I'd like to make to the old machine is a VFD for the
existing 5HP motor and some sort of breaking system (poss. built into
the VFD).

Are you thinking of buying one?

Turner