My 47 has an IND 32 (265 cid) from around 1970 which has sodium filled exhaust valves. I bought the motor from a guy who had a pair of them in their original crates. As he explained it, they came with a snow cat that he had bought at a county auction somewhere in New York state. The municipality bought these pieces of equipment and wanted 2 of everything including 2 spare engines. That's how I got mine. The guy wanted the snow cat but not the rest of the stuff that came with it so he listed them on Craigslist. Anyway, these weren't for a stationary application. I would check to make sure that the valve guides are the same for the 2 different valve types. If they are different, you could be opening up a can of worms trying to find the correct ones.