You will be able to tell if it has hard seats. After you remove the exhaust valve, clean the area real good and look for the OD of the seat. If you can see where the outer edge of the seat meets the chamber. It has hard seat inserts. But, back then even the hard seats they used (hardened cast iron inserts)were generally not good enuff for hard use on todays fuels. Todays seats are usually Sintered (powder cast) or stainless/stellite alloys.

If you plan on any kind of towing or use other than a driver. Have hard seats installed. Do use the Stainless valves. Lighter, tougher. They will also show less seat pitting and erosion. Common with modern fuels.

PS. If you need this engine bored. Most small machine shops will not have the spacer used to bore a 348-409. Unles they have a diamond head in a CK-10 or CV-616 type machine. They will need the spacer for a regular boring bar.