KC2YU, got your e-mail on KD6TH-4
The Motorola HT220 I modified is on 2 meters.  
They do make good packet radios.  

Although I can't give exact procedures, I can mention some 
things that I did (as your radio is a different model).
I found that the little tx/rx relay is quick enough for packet.  Time
from tx to recieve is fast enough that you won't miss the beginning
of reply packets.  I found that rx to tx time is reasonably quick, but
I told the TNC to make TXDelay a little longer.  I found that I can 
drive the relay directly from the TNCs PTT line.  (ground PTT to 
xmit).

The reciever may be a bit slow to unsquelch upon recieving a packet.
So I leave the squelch open, and use SWDETENA ON on the TNC. 
 
 I used a preamp in the mic line, to boost the TNC mic audio some (about
  7dB).  I could have changed the TNC level by changing voltage 
  divider resistors but this would make it wrong for my other radios.
  But be careful to not overdo it!  
  I've heard it said that one is better off with the xmit modulation
  at a somewhat low volume.  You get less distortion that way, and other
  TNCs can hear your packets better.  Works for me.  Using another radio 
  to listen with, listen to yourself transmit a packet.  Compare that to
  other stations.  Set the modulation control trimpot so that your packet
  volume is a little lower than most of the other stations you hear on 
  the air.  (I mean about 2dB lower). 

  You should mount the radio pcb in a metal box.  And use bypass 
  capacitors on every wire leading into the radio (except the antenna
  :-) ) This is to try to keep the TNC and computer RFI from the radio
  reciever.  Try ferrite beads too.  good luck!

  I used Ethernet coax for the antenna line, outside of the
  metal box.  You may need to retune the radio's finals to load into a
  50 ohm antenna, instead of a duck.  My antenna is about 20 feet
  overhead in the attic.  Depending on how close you are to BBSs, etc, 
  and if you live on the top of a hill (like me), you might get by
  with the 1.8W the radio puts out.  The Ethernet coax is like RG8, a 
  low loss coax, which helps with low power. It has excellent shields.
  My radio has a power amp that makes
  7W.  It's in the antenna line, like a linear amp of HF radio.  In my
  case, my radio's previous owner put it in, so I can't help much here.
  To get recieve signals to the radio, I believe he used a  pair 
  of 1/4 wave lengths of small diameter coax and pin diode. 
  Not clear on this.

  Hope this helps,  73s   Bob