My 383 will be going to the machine shop this week hopefully. not going nuts, just a little better than stock. .030 over, stealth heads, 9.0:1 compression. I want to run low grade pump gas, and be able to drive it as far as I want whenever I want ! I spent quite a bit of time comparing bone stock rebuild vs mild upgrades, buy the time you add up all the stock stuff its really not much more to add some performance upgrades. stock iron heads with good seats, seals, bigger valves, machine work was not much cheaper than the complete aluminum heads. you wont need to run lead additive, just have the heads gone through and hardened seats installed, you'll be fine with that ...