I don't know for sure about the "lead" question for the valves. On the recommendations of others, can't recall whom, I ordered the RedLine lead substitute from Summit (or was it Jeg's), and did use it. The valve seats are of '40's standards, and may be more protected with "lead". I just had my engine completely re-done by a machine ship, and part of that was new modern valves, and hardened intake seats. He said the exhaust seats, which are hardened, were fine, he just cleaned them up. So I have some "lead" left over, but don't plan on using it. Although, I don't suppose it can hurt, and may use it in my "power-products" if not my 37's engine.
In my small SC city, there are lots of stations now who sell non-ethanol gas, perhaps for all the folks who are in the business of mowing lawns and such. So for sure I use it in my own mowers and other piston tools, and also in my truck. My understanding is that ethanol can corrode or otherwise damage old parts like carb's and such. I just spent thousands of dollars and hundreds of hours re-doing my engine and other parts, so spending a little more for possible added protections is sure worth it to me.
Actually, if I can recall, someone at Vintage Power Wagons suggested a concoction of Rislone, Seafoam, and lead substitute, and if not driven regularly, Sta-Bil in the gas, if the engine was original. My truck ran fine on this, before my complete re-build.
So I cannot say with any authority or actual expertise, that adding a "lead" substitute is necessary or not. But my thought is that lead is cheap, engines are expensive.
Your choice,
NAM VET
Be careful of the intake and discharge balls on pump circuit and you'll be golden (you'll get replacements in the rebuild kit, don't worry if you lose them during disassembly). 
