J31 Tpe331-10/12
I used to be involved with this aircraft type many years ago.
Ignore any ex RAF aircraft and HP 137's with the Astazou engines, you want the Garretts.
Earlier Garrett -10 engines, if my memory serves, had a torque measurement system that utised oil pressure and could become expensively unreliable. You are better off with later engines that used a strain gauge system.
I also seem to recall that the inverters on the earlier aircraft weren't so good. Again from memory you want a post aircraft 650 build number.
'fraid that's about all I can remember at this time of night.