How about your garage?
Seriously, the Rootes Shop Manual says the calipers should never be split. However what's the magic in loosening 4 bolts, cleaning things up and then reassembling with new parts? (all the parts are easy to locate.) Proper torque is necessary and there is a difference in the torque on the inner bolts versus the outers.
We've split Tiger calipers on the race car a half dozen in just one season. Never had a rebuilding problem. Remember, the bore on the caliper is relatively unimportant since the seal surface is the outside of the piston. You do need to clean out the groove for the seal in the bore but that's easy with a dental pick. I recommend stainless pistons like Rick sells. These can usually be reused time after time after a very fine sanding with wet sandpaper & a light buffing. We assemble this with clear silicone grease.
The hardest part of the job might be just getting the calipers off & back on the car and bled properly. (You'd still have to do this part if you had them rebuilt.
If you have any questions, feel free to PM me.
good luck,
bt,
at the beach