yes thwre are 2 different 6.4s in the trucks. this is why the bge was considered the 1 to get over the other 6.4 block. you may want to check the head casting numbers to verify if they are bge castings. phyically the bge heads are a lighter color shade almost a polished looking aluminim vs the other darker dull shade of casting color. quick visual difference if you have any other g3 head laying around to compare.
the bge heads are cast with the same type of aluminum as an aftermarket head. all others are of an inferior cast aluminum. that is another reason for the bge favor over the rest.
the HD 6.4 was the bge thats wht the HD was designated. it was doen in power but much more reliable design.
