Yeah, I'm hit with a bit of insomnia too. :)
A:
No. If you're keeping the car and especially if you're driving it in hot weather, it's a good thing to have. Hell, a/c is also handy to have in cold and wet weather too, for keeping the windows unfogged.
B:
You
could try finding a system from a 140, but you'd be far better off finding a system from a late model 240. The heater box unit is pretty much identical from 1973 through to 1993. You'd be better off also with a late model compressor. However, that may mean fabricating a bracket to fit the B20.
C:
Not yet, but it's firmly on my agenda for Xoe and Chloe. I've already purchased a bunch of bits from
@Angus242164 and
@davem to make it happen.