rpm airgap vs the m1 single plane

Here is a little info on my engine
Kb190s with the xheads I think it is a little over 10 to one
Mopar 508 cam with hughes 1.6 rockers
4 10 gear /727 trans Rmv /4200 dynamic converter
Really old inch and 5/8 headers / m1 single intake
No power steering or brakes weighs. 3300


I do have plans for building a 408 / I was justify the air gap cause I think I can use it in both engines
L