Most everything is different between the PASS CAR and BIRD, due to track-width.
I guess I am a purist, I want it to as it was built (as possibly feasible) especially if it is a nice car. I have no use for a JAPANESE steering box or CHI-COM electric steering. If I want to go to positive steering control and was modifying the car for resto-mod or hot street, it would get a MUST II conversion.
It is all up to the owner and what he wants.
In a case such as this where old parts are becoming a problem, it might be best (IMO) to find a salvage car, strip it and dispose of it.
Even if you do find a donor all the hydraulics will have to be gone through and mechanicals most likely.
When you take into consideration the BIRD KIT and all one would have to go through to convert one, it is a good deal (IMO).