If you have a slicer with an isolation cap, you can tap directly to Pin 9 of IC 2. Trace the circuit to R44 and solder your tap at that point. There may also be an unused solder pad between D45 and R86, which will also trace to pin 9.
Download Pete Crapi’s SM-2 of 4 zip at
http://groups.yahoo.com/group/PRO-2052/files/Service Manual/
and go to page 22 in the pdf for the location of R44 and the trace to pin 9 of IC 2. I use a ground near the antenna ground point and mounted the jack next to the antenna jack.
Read the Trunker doc, then read it again and maybe again.
The Trackenv.txt will be the key to getting it to run correctly after hookup.