Yes, there were LP conversions for Chevrolets, mostly 235s, but V-8s later. Yes, the original valve seats don't hold up very well under heavy load; light load/passenger car service seems better, but still not without risk. Hard seats are advisable. Also, the heat riser in your engine is not meant for vaporizing LP- there is a 'vaporizer' for that purpose. I don't think it is worth the trouble to make that conversion, given the potential for trouble, even though users in the past claimed longer oil life (probable), longer spark plug life (generally true), better fuel mileage (doubtful), and more power (imaginary unless you want to recurve the timing advance mechanisms, and you know what you are doing). The better fuel 'economy' was mostly referring to the lower fuel price, compared with gasoline.
LP conversions became popular during the 1970's, but they didn't last long with the public, after the public got some experience with the inconveniences and troubles that often came with that conversion.
I would advise staying away from an LP conversion for your 216 engine. Others may differ with that view.
Harvester
