I like the wow factor,that's why I asked(and it says mopar performance) and also perform alitte better,would the M1 single plane work good on the low end of a 4" arm 340 and how about under hood clearance issues,thanks.
M1 has same flange height as stock and Edelbrock RPM.
M1 single plane will generally loose some low end TQ and HP in mild street 4" stroke motor. And the dual plane will idle a little smoother and easier to tune. If you have a good tunable carb and you are on top of your tuning abilities, you can get a nice idle out of a single plane. Sort of depends on your cam really.
I use the M1 single plane. But I'm willing to give up some low end for more high end at the road coure track. Car does not hook up great on the street with the stiff suspension, stiff tires, etc anyways.
But I do have a Edelbrock RPM ready to go on the the shelf waiting. I scored it for $80. About $40 less than the M1 I got off ebay.