Well, I just cruise along in my XJ40 LMAO while everybody else is bored to
death driving their Toyotas.
I would say yes to reliabilty. Mine is from 1992 and has done 155000 km now.
Since I bought it last year (25000 km ago) I have replaced the windscreen
washer pump and changed oil, belts and filters.
The difference between 1987 and 1992 could be significant I guess, as Ford
took over in 1990. Mine is sealed everywhere in the electric system and
seems to be very well protected against rust. Spareparts also seems to be
quite easy to find as well.

Check this:
Ride level control at the rearaxle could be a problem. Load it and check
that it gomes up after a while. Mine is SLOW, 2-3 minutes driving is needed.
Maybe this is how it is intended to be ?
Rust everywhere off cause. The front axle body is filled with foam to reduce
noise, check it...
Funny sounds from transmission and suspension will cost you some day
Low oil pressure at idle could be a faulty sender unit. Idle pressure is 2
bar for a new engine. Some units has been replaced by a new model sending
the needle to appr. 4 bar regardless of pressure as long as it is higher
than an absolute minimum...
All electrics should be checked for function. There is probably a lot :o)
Radiator and hoses will be critical on a car almost 20 years old.
No timing belt, it has chain drive.
Pumps and alternator are driven by external belts, easy to change

Good luck :o)

Leo Jensen, Denmark