I need to ask the engine gurus of the list a question: Does an STC for drilling a solid crank Lycoming O-360, to allow installation of a constant speed prop, exist??
I think you would want to exchange for a hollow crank instead. Depending on your engine model, there may be additional changes to the case, accessory drives, ect. It might not be worth converting your engine, keep it simple. Contact a large shop like ECI, tell them what you have, and what you want to do.
Thanks for your input Mark. What you say makes a lot of sense.
(It isn't my engine, nor my project. It is a 'homebuilder' customer of an A&P friend. The guy bought an engine that he shouldn't have bought and now he is asking if it can be modified to suit his purpose.)