The are a number of different brake options that I have seen on various ERAs. Bob Putnam can advise as to what fits and what does not. (See:
http://www.erareplicas.com/427/bigbrake.htm)
As for the rears (assuming you have the inboard Jag. setup), I did go for a vented disc that utilized the standard Jag caliper, albeit with spacers for the wider disc. See:
http://www.xks.com/shop/jaguar/ACCDe...spx?catID=5136
Jim
PS: I have Sierras on my FIA with ERA's outboard brake rear. The Jag. vented disc setup went on to my cousin's ERA427SC.