I was thinking of using Ocelot's "Sewn by hand AVR" Article (in Russian, but the Google translation is here: http://habrahabr.ru/post/152052/.
You can see a video of someone (Ocelot?) doing this at:
https://youtu.be/UJHeDvr_doM
Ok, so maybe I am a little strange...
The 10x's and 200 all have built-in BASIC, and should be able to do the actual programming. And, I have a TPDD2 (Tandy Portable Disk Drive 2) which could store the program and data, but it would quickly get cumbersome. Unfortunately, the 600 does not have the BASIC ROM chip. Do any of you happen to have a good working image of the 600's BASIC for the disk drive (the 600's drive, not the TPDD.) Then, I could write the entire "tool chain" and do full AVR development on an old Model T. I think that this would match up with my Tiny2313 dev kit (http://zappbots.altervista.org/forum/viewtopic.php?f=44&t=103) pretty well.
It's been pretty stressful here (currently unemployed for 15 months,) and I need a nice relaxing (FREE) vacation. I already have everything for this kind of project, on hand, so I can actually afford it.