What fuel should I run in my 340?

gas octane ratings have changed since our beloved MoPars rolled-out of Detroit ( or L.A. , or St Louis or ... ) .

gas used to rated in the U.S. by MON : Motor Octane Number ; this is the higher number .
in Europe , gas went by RON : Research Octane Number ; this is the lower number .

"R+M/2" = Research octane number + Motor octane number , divided by 2.
So , let's say your typical '68 - '71 340 has its 10.5:1 comp ratio . This indicated the need for ~98 octane , with optimum performance from 105 octane ( "Premium" vs "Supreme" ) .
When "R+M/2" was introduced , 5 octane points were relinquished ; 98 became 93 , and 105 became 100 .
So , today's pump gas numbers , equating to their new vs old ratings , are :
87 = 92
89 = 94
91 = 96
93 = 98
94 = 99

I'm not sure whether or not racing gas still goes by the old MON rating ; does 115 actually equal 115 , or is it 110 ?