I have just finished updating my ARK-40. For those not familiar with the rig, these were offered in the 1990's as monoband CW rigs with a synthesized VFO. Models were available for 80,40,20 and at least some for 15M. Wonderfully well built and a joy to operate except for the thumbwheel tuning. I never could get used to it.
With W8ZR as my inspiration (see http://www.w8zr.net/homebrew/hbark40.htm
), I used a Basic Stamp module to convert an optical encoder output to the 14 BCD data lines that the synthesizer required. The stamp then also was used to drive a backlit LCD readout. Upon power up, the radio first displays an ARK-40/W4OP splash page before setting the synthesizer to the QRP calling freq 7040KHz. In this mode the encoder tunes in 1KHz steps for fast QSY. By pushing in on the encoder knob, tuning and display are in 100Hz steps- the finest increment the synthesizer allows.
When I got the rig, a previous owner had ruined the front panel in an attempt to move the keyer speed pot to the front panel- what a mess. So the rig has new life and has been a lot of fun on 40M CW.
Here's some photos of the conversion:http://www.parelectronics.com/vintage-ss-engineering-ark-40.php