I used half washers for quite a number of years. I think that is the way they
came in the 1968 models that had double downpipes and aluminum intake manifolds.
(at least I found some appropriate half washers in the lot of parts I got from
a fellow who scrapped one out after his friend ran it over a high curb on the
Bridge of the Americas (over the Panama Canal).
Later I took all my manifolds over to my friend's machine shop here in Bartlesville
and he spot-faced the offending holes to the right thickness for the aluminum
carb manifold. This has one potential disadvantage: If you want to use the
manifold for a fuel-injected engine you are back to half-washers for the exhaust. But it looks a lot neater than the half-washers and is MUCH easier to install!
--
George Downs Bartlesville, Heart of the USA!