Natural to LP gas conversion

Previous owner of this cook top states that this unit was converted to natural gas by the local gas co. (PG&E) by simply adjusting the gas valves, but she also said it was 3 or 4 years old to, so maybe not too accurate? (It is dated 0-0-91) We wish to use it on LP. The regulator on it is a Maxitrol, numbers on it are 0239 137 and it sure looks like it has been field installed. The valve orifices also appear to have some light wrench markings. Maybe field changed also? Are the correct orifices available, and is changing this top back to LP worth doing? Wondering if the LP regulator currently serving the existing 4 burner top we wish to replace will be satisfactory?
Any help will be appreciated!
The question mark in the Model No. is because it has been written over by hand. It might be a "B".
Thanks,
Art