For TM500/5000, they are basically only power rails, along with with ECB to power transistors. I guess the plug-in specific top pins are not so much needed for repair.
In particular, some power pins are duplicates, for example, the 4 common return pins for 8V/11VDC for instance, a single 22 AWG wire will do.
For the 7000 series plug-ins, there's just too many pins and are almost all used.
So I plan to use some ribbon cable, with may be some individual wires for power (i.e. +/- 50 & 15 VDC), and some coaxial wires for the signal pins.
These are readily available at Farnell and Mouser.
I've not much experience in RF signals, but I guess that with coax on the "critical" signal pins, that should be sufficient for <= 100MHz, maybe even calibrating.