they should be fine, its the thread and obviously the flat but at the end to make a seal that is important. if you cut them nice and close you can use a socket to remove them without rounding them off, 11mm i think, maybe worth chucking a bit of wd40 at them 24 hours befor if you can and give em a lick with the wire brush too to get any loose dirt/rust off helps to keep the crap away from getting in and causing any probs!!!
guess it should only take about an hour.
one thing to have a look at(it happened on ALL of mine) is the caliper bolts onto some sliding pins on the brake frame. mine were seized but only on one of them, the same one on all four, top on one side bottom on the other. if they are, go to the scrap yard and get some more, most rovers fit, mg's and the rover 75 front fit both front and back on the rr p38(at least the one i have, 1996my) at least be prepared to go get some as they shear quite easy. i know it happend to me and the blind panic was enough! even if they are free take them out and give em a rub down with wire wool, re grease and put back, chack pads too, doing this stopped an annoying squeak i had on my car, also i slapped a bit of grease on the wheel bearing(the one connected to the chassis) dunno if it will help, just for protection and a bit of belt and braces approach.
i know its a bit long winded but prevention is easier than the cure!!!!!!
HTH
Gav