Breathing new life into the 318 in the Scamp!

I would strongly recommend putting away those head gaskets and getting some 1008 gaskets, they have a compressed thickness of .039" which will give you much better quench than the 8553s... your compression will be a little higher but it will actually be less detonation prone. I used those gaskets and with the heads on my 360 (but bolts not fully torqued) actual quench distance measured at .045".

Look at it this way, with KBs your engine will be basically the same as mine and I run 87 octane with no detonation unless I punch it when it's hot and sunny outside. Your engine due to having a smaller bore will have at least .5 less compression so it should run even better on pump gas. Also take into account I have my timing set at 16* initial and 35* total which is a bit on the aggressive side; bumping it down 2-4* would probably allow me to run 85 octane if I had to. One last thing you mentioned you will be running 3.91 gears with the O/D trans, that will give the engine a lot more leverage accelerating compared to my car as well with the 904 and 2.76 gears which will also reduce detonation.