The MOE is made to work with an "F" sight base, standard military front sight.
I am guessing the wide part of the GB was the problem?
Any carbine length rail will work but, if it isn't a 2 piece add on you will have to remove the barrel nut to install the free float rail.
Check Midwest ind. or YHM
Hi perf barrels and bolts
8 twist, 5R, Melonite, Wylde chamber