Fred, Looks like you're covered. If you need more info, perhaps I
could help. I have the AF training pack for the unit as well as the
original Collins book. As one who's gotten one on the air (sic), I can
tell you that there are a few points to ponder. Hopefully you have at
least one tuner. If there are no tuner, you can build an external
network. The big thing for most of us was/were the L/C tuning elements
for the receiver and transmitter. The rx requires two elements (mixer
and RF)and the transmitter one (driver). They plug into the boxes in
the middle of the unit and screw down to a horizontal bars. Originally,
the tuning elements came in a large kit and are set up for chunks of the
HF band. I was unable to find any elements, whatsoever, over about a
year's worth of looking. I ended up putting three together for just 80
meters. As you may have gleaned, the 18-S is pretty much an ART-13 and
simple receiver, sans the VFO and ability to variably tune either the tx
or rx.
Racks are unobtainium (unless, again, you got one with yours). The rear
connectors can be had from the Wm Perry Co. for about $20-$25 each. I
do wish you good fortune with the project. FWIW, I can tell you that,
although they did work OK when properly set-up, the AF techs cursed the
radio set and were pleased when the ARC-38 and the 618S equipment came
into the inventory. The 18S is said to be a stop-gap to provide for
compliance with the emerging ICAO requirements. Interestingly, I have
copies of the Proceedings which address the HF aeronautical spectrum in
the early 50's and the recommendations and requirements made back then.
Regards Jeep/K3HVG