Dual plane, assuming ld340 but it's not cast into it. It is an old piece, converted in the 90's and ran as a carb years before.
Not sure on mopar, was there an m1 dual plane for sb?
Looking for a ready to go shortblock or longblock, RB based 440-540". Pretty flexible but looking for a street friendly engine so nothing too radical. Solid or roller cam is fine just not a monster one.