Here’s a past post on both the hardened seats and the lead additive.

Adding lead to gas

Lorena, Texas (South of Waco)

Todd: first, are the heads on or off the engine?.. If you are having them redone, best put in hardened exhaust seats. If you are driving it "moderately" & it runs fine, just leave it alone until other major work is needed..

Paul

Put in the right valves, you will have to do it sooner or later anyway. Welcome  55Birdman

55Birdman  Hickory NC

                    Ok I am new to this site and maybe this question has been asked before, I am not very experienced with the y-block, my question is the y-block heads do not have hardened seats to run unleaded gasoline do they? and if they do not what would you guys recommend for a lead substitute? thank you for the info!

Todd Watertown S.D.