I refer you to Dave Rhoads 64 with 82 X 88 and 12.40's at 106.
Great motor, but good luck on finding a set of stroker 88's.
I've known of a couple guys who built 85.5x82 motors (custom pistons). Good mileage, but overall performance seemed a little boring and it was alot more work than simply throwing together a simple 1915.