What stroke you want to run with those cylinders? I've seen a K&T 10mil with stock cylinders (quite a bit of epoxy work though) that was well above 100hp. I would think you could achieve 100hp quite easily with a 4mil and a good drag port. But remember its a complete package, not just cylinders or stroke. Carbs, pipes, intakes, dome design... there's a lot that goes into getting a good running package. I would think a 4mil drag port would be an excellent start. I'm sure it could be done with stock stroke as well with a good builder.