the 318 BBD as is DOES work fine. i did it way back in 1975. but do be car full to NOT over tighten the the two long screws that go from the top casting to the bottom casting. or the castings will warp. make a steel plate to mate to the 2 BBD carb. do NOT weld it to the stock manifold. grind the raised spot for the 1 BBL to flat to the rest of the stock casting. and bolt it with countersunk screws. and make the 2 BBD shaft run parallel to the crankshaft. and be VERY carfull that the linkage does NOT lock the carb open when done. it was like adding a second engine to my 1964 dart , and NO loss in MPG.