The BS story that leaded gas cushioned valve seats was a scare-tactic made-up by the petroleum industry in the mid to late 1960s because they wanted to continue using lead as a cheap way to boost fuel octane … in spite of the public out cry to remove lead from our environment. There was no truth, substance, or proof to the petroleum industry's claim. The cars from the 1960s continued to operate just fine after lead was removed from pump gas.
I've never had to put seats in a Cleveland cylinder head … any head I've disassembled the seats were in great shape, the valves is where I discovered wear … and that was with OEM iron seats.
I owned a Mach I Mustang, drove it as my daily driver for over 250,000 miles. The engine was still running strong when one of my sons crashed and ruined the car. No valve seat issues had developed in that 250,000 miles.
Cleveland seats need to be installed "shallow" to avoid hitting water jacket. The probability for ruining the heads while installing seats is high.
However, if you're going to install seats, install seats that are compatible with the valve material. Stainless steel is not a "hard" or "tough" material. I put stainless valves in the same class as titanium valves. Use iron or beryllium copper seats, never hardened steel. Same reason valve guides should be either iron or bronze alloy.