Hi,
For my TR4 I got a body installation kit from TRF and was happy with it. Some of the shims or packing materials were reinforced rubber, assorted circular and rectangular ones, with sort of a canvassy material in them, if that's what you mean. Particularly at the outriggers, more or less of those packing shims can be used to help align the doors.
I don't know about TR3 outriggers, but on TR4 the body bolts down with a standard 5/16 NF bolt and a rather thick and oversized washer.
BTW, when removing the body from the TR4, I cursed to find a previous owner had removed all the washers on the passenger's side outrigger bolts.... I have no idea why!
Anyway, for a while I really struggled trying to get the bolts out, since they had pulled into the rubber shim packing and were recessed into the holes in the body... Then it dawned on me! This was not one of my finer automotive engineering moments! D'oh! Those 8 bolts weren't holding anything, they'd already pulled through the body holes and I didn't even have to remove them to lift off the body! Geez... All that cursing for nothing! Removed all the other bolts from the various mounting points, lifted the body and later removed the washerless bolts easily, once I could get a socket or wrench on the heads.
By the way, the TR4 shop manual shows some sort of body seam sealer used under those outrigger washers. Probably would be a good idea to use a bit of it on any TR body to frame mounting points. If nothgin else, it might help keep the bolts from rusting and make them easier to remove the next time you restore the car, say in 25 years or so.
/ubbthreads/images/graemlins/cheers.gif