thanks for the web link to that tetra-ethyl lead supplier,
I will add that to my archive

Here is an archived article with info on another tetra-ethyl lead supplier that may (or may not) still offer it in bulk:

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Lead additives
Chicago Tribune, Motormouth columnist Bob Weber

Q - Do you know of any sources for purchasing a lead additive for antique
autos? I picked up a 1963 Wildcat convertible in excellent condition with only
53,000 miles on it. I also have two friends in a car club who are interested
in a lead additive. They have'52 and '56 Cadillacs. We each drive about
600-1000 miles a year.

A - Gasoline used to contain a compound called tetraethyl lead, but due to
health hazards, it was removed. Although you cannot buy this stuff over the
counter, I found a distributor in Columbus, Ind. that sells it by the gallon
($22.95 per gallon) by mail. Although it isn't cheap, about 12 ounces treats
20 gallons of premium gas. "Max Lead 2000" is available from Vogel Products,
812-376-2775. They offer quantity discounts to car clubs.

There are other products available at most auto parts stores, but they are
lead substitutes and may contain a variety of other chemical compounds
including phosphates, sulfates, sodium and so on.

However, with as little driving as you and your friends do, and considering
that you probably baby your cars rather than race them, you probably need
nothing. Your engines will probably see no valve recession for many, many
years.
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