Alternative Fuels

What is the octane rating for propane and butane?
We have a summer mix overhere 40% propane an 60 % butane In winter it is 60% propane 40% butane.
And how do I convert this to the US fuel rating?
Building a supercharged 6/71 454 and try to figure out what the max boost can be with the 7.3 compresion ratio that I have,
On us pump gas what they call 92 that is about 97 here in Europe The rule is do not go over 12.4 final comresion.
Will use a intercooler between the SC an intake, hope that I can get into the high 14S final compresion.
Have all the good go fast parts. Aloy heads forged crank and pistons H bean rods 4bold mains . etc
Thanks

Butane has a RON of 94, Propane has a RON of 110-112. 50-50 split would make it RON 102. 60% B - 40% P would make it RON 100, 40% B - 60% P would make it RON 104-105.

To convert that to the AKI you need to know the MON rating and then you calculate it with (RON + MON) / 2. This usually, but not always, gives you an AKI of 4-6 lower than RON.

Thanks,
Sorry for the late reply.