I am a believer in the same LSA for all rpm ranges, because the heads flow the same at overlap. As duration goes up or down to suit rpm range, so does overlap duration. David Vizzard has done extensive testing to confirm this. Sooooooooooooooo, just WAG on my part, but an lsa of roughly 106 with about 232 @.050 on both sides might work well. If the recommendation is for more exhaust duration, then the LSA is just wide enough to get back to the same overlap duration for best results.
A call to a pro is the real answer, since you have a very special need and a few more $$ is very well spent. Dwayne Porter of Porter Racing Heads frequents this board, and is really sharp on cams. He can have one ground to fit your exact requirements.