Marvel mystery oil used as a lead substitute?

Ok, i know the subject of weather a lead substitute is required is a bit controversial So maybe there is two parts to this question, the first would be weather or not a lead substitute is actually needed on a early v8? The second is i have read that you can use a capful of marvel mystery oil to a tank of fuel to add the required lubrication. So here is the situation the motor in my 56 Dodge ( that I installed ) is literally a time piece , it was pulled from a 1970 Dart with 12000 original miles, ( the owner installed a 360 in it ) then the car was sold and the new owner didn't want the 318 which was a perfect donor for my 56. The engine is so clean it looks like it is new. I've had it for many years but as I posted on this site earlier this year I finally got my 56 on the road. The only thing I did to the motor was swap the car oil pan for a truck pan and swap the 2bbl manifold for a Eddy 4bbl one.The engine runs beautiful, no smoke , ticks etc. I primarily run Chevron 87 octane ( with Techroline additive ) sometimes I put some 94 in just because. So many say you MUST use a lead additive as my 1970 valve seats and guides will not be hardened others say it's a myth? I'm not sure I'll ever no for sure the answer to that. But I know there are lead additives you can purchase but some say a capful of the Marvel Mystery oil does the same thing? AND I have three large bottles of it. I don't put a lot of miles on this truck it's just a fun toy I drive a few times a month in the summer. What say you????