I had the same rig (1976). Took a lot of soldering to get it together. Ran like a champ for years. Loved the audio tape storage (Kansas City Standard). There was a public radio station that occasionally broadcast programs over the radio that you could save on a tape. Hauled it around for about a decade before ingloriously ending its life in a dumpster.

I experience severe wrist and arm problems a couple years ago. My ergo department let me experiment with a lot of different solutions including the foot mouse. I found it very tedious and difficult to use for programming. It was very hard to do any exact pointing and I found myself with my feet tensed up, leaning back in my chair trying to get the cursor where I wanted it. This was making my back ache and wasn't particularly relieving my wrist pain. I finally settled on the roller mouse http://www.contourdesign.com/rollermouse/ The design slips under a standard keyboard and provides a sliding roller near the spacebar. I found I could quickly point the cursor just about anywhere with minimal wrist movement. It has really contributed to my quality of computer life. I liked it enough to get one at home too. Your mileage will vary.