Im looking around for a driver side door for my nephews 91 Rex and Im unsure that the years are interchangeable. If someone has a definite answer please chime in. I was looking on ebay for prices and saw one for a 88' but the seller claims it will not work for a 91'.

 

The 90 and 91 CRX doors have the seatbelt mount on them... the 88 to 89 years had the seatbelt mount on the body to the rear of the door.

That's really the only difference I can think of.

EDIT: I take that back... 88 doors had no seatbelts for all models, and 89 HF was the only model of that year which stayed the same.

 

From what I heard the fitment is slightly off. So when you driving you can hear air coming through the door seals

 

The vertical trim piece on the exterior behind the glass (might be called a sash?) is also a different size.

 

crossreference the part numbers on hondapartsnow.com. That is your definite answer. Trim can always swap over.