Are you talking about adding propane to the existing gas burner or going full propane?

If you are considering as an adder, it's not the best option.
Nitrous would be a much better option. Propane is a good
replacement for nitrous in diesel applications, but not
really that good for gasoline.

If you are considering propane as the primary fuel,
propane is not as efficient and as gasoline as far
as producing energy. Yes, you could increase the compression ratio, but I doubt you'll get anywhere near
the power output on propane as you would gasoline.
It would be a very clean burner compared to gasoline, but
would most likely be a pretty good loss in power.