Fo materials, it's all personal preference but I love the vinyl side bolsters with a cloth center. It has a very nice feel to it.
Another nice touch is to recover the door panel inserts to match in the same material. It's a shame you have a 1991, because up until 1990 Ford made those insert panels removable. You can take them off and cover them to match the seats. That's what I did on my car. You'd need to track down some black 1990 panels to do this however, but it's a good touch for sure.
Definitely make sure whatever you cover the centers in, you buy enough material to do the rears later on or the panel inserts. That's the problem i'm having right now is I can't find matching material for the rear. I almost need to buy another set of inserts for the front in good shape, pay top dollar for them, and use that material for the rear seat. Obviously I haven't done this yet. My door panel inserts are a close but no cigar material