Safety Devices in the UK makes external cages for the 90, which I believe can fit the 88 as well.(worst case, the long straight bars traveling the length of the roof would need to be sectioned slightly; if you tell them it's to be used on an 88, they most likely have the correct kit for you)
I have a SD full external cage on my 110 regular, and I mounted the roof rack directly to that. On my 88, the roof rack destroyed the roof in North Africa; it's too much load for the roof. After that lesson, I knew it was imperative to have the rack mount directly to the roll cage.
For the Camel Trophy, they used a Brownchurch heavy duty rack (modified for the event). The HD rack uses several extra supports, two in the rear which bolt through the tub capings on either side of the rear door, and two in front which bolt through the windshield mount brackets and all the way into the cabin area (these replace the hinges found on the soft top models).
My truck was originally fitted with a modified Brownchurch HD rack, and the holes were there. I filled them with bolts to stop some drafts on the Arctic Circle trip I just did.
If you can avoid it, don't mount the rack to the roof rails. And, regardless of how you mount your rack, load it LAST, and with the lightest things you can put up there (NOT tires, recovery chains and fuel cans). Always load the truck first; heaviest stuff lowest and work up from there. Not always the most convenient, but the safest way to go. Also, secure all cargo, inside as well as on the rack. It might just save your life!
Owner: James Leach Global Expedition Services.
1995 110 Regular