Hi,
The manufacturer specific signals are really there to enable the Radio's tune button, and get the good/bad status back.
All the protocols are different (different voltages, and different signalling/information).
Some of the manufacturer's ATUs use these signals for band/frequency information, but the LDG/MFJ ones are pretty generic.
If you give them power, then they will work fine with just about any radio, as long as you use the tune button when needed.
(I've used a K-100 with a 12V power cable soldered to the main board, on Icom/Yaesu radios with no problems).
?
Roger.
RogerW/GW6HRU