Blocking
Hello, I've been blocking off the heat passage since the sixties on 348's. I just go to the local hardware store and pick up a thin sheet of copper and trim it to fit. Never a problem burning through or leaking. You could give it a coat of header paint also if you plan to never pull the intake in your lifetime. I also have always run a 160 thermostat on my early 58 348's. Don't know what insulating carb gaskets are out there to use on 4 barrels.Anybody? Used to run a pair of 409 AFB's on a 425 Olds back in 72 in Minnesota , so with the heat passage blocked in cold weather I recommend a manual choke if you need one. Takes a lot longer to get an electric choke to come off in cold weather without the extra heat. I would be glad to install for you and test drive for a year if you need help!!
Dave.