Hi,
I just came accross this thread.
I purchased the complete Ft301 line back in 1979 still have it brand new and in boxes. In the early 90’s I purchased a bunch of the IC that get programmed for the FP301D.
I looked into this as well and have schematics to make the programmer for the 74188.
Feel free to contact me I would love to get this going again.
There are other FT-301 groups on (groups.io)
KD6UJS
MIKE