As far as I know the Raidens had a prototype of each version, i.e. m1,m2.m3.m4.m5,m6.
To build the J2M1 prototype the cowl flaps have to be seriously modified as well as a few smaller details.
You might check out the Mushroom modeler book on the Raiden as it has some of the best info on all the versions.
Hope this helps.