With the headliner out there wasn't going to be a better time to do this, it is also possible to fit the antenna by just removing the sunroof motor cover..
Purchased the antenna kit from 928Intl, evidently this is a generic Fopar kit but accessory shops up here arn't that well kitted out. Everything you need except the drill bit.
On my 87 there was already a slot in the inner sheet metal, it wasn't big enough to put the nut for the aerial into though so out comes the Dremel, I made the hole large enough to get the nut through but the key is to lengthen the slot so you can get a wrench in to grip said nut. As you can see from the photos it ain;t pretty but all the sheet metal contours are in the wrong place !!!!
After smoothing off the metal adges I got some undercoat paint and touched up the bare metal, Ok the Dremel can be put away now !!!
Now for the bit I find hardest, drilling a hole in a perfectly sound body. Need to drill a 5/8" hole (15mm) which wasn't a nice size to fit in my 3/8" drill chuck, then I found this neat drill bit at Home Depot which will drill progressively larger holes upto over 1" in diameter. Its expensive ($30) but it did a great job and no hassle.
Now I painted the exposed metal again and after frying coated the area around the hole with the grease supplied in the kit. Inserted the aerial and got the nut to start on the thread. One arm through the sunroof opening works best, once finger tight I got the wrench on the nut and rotated the antenna backwards and forwards.
Routing the wire again was easy as all my interior was stripped, need to do some fishing with string and a coat hanger if you were going to do this without at least removing the rear quarter. I noticed on my 91 that the connections to the wiring harness are wrapped in foam, I will do the same as the last thing I want to install is a rattle.
I like the appearance but I also know that when my windshield needs replacing I can get the cheap(er) one without the integrated antenna.