[Brian]

I've posted this before, but here we go again....some years back my trusty old 35 would fire up on 8 cylinders, but the longer it ran, the more ragged it ran, until it would actually die. i was convinced it was electrical; as the components heat up they misbehave, accordingly I changed condensers, distributors, coils , you name it, all to no effect. Sparkplugs all looked the same, compression test showed all cylinders within 5 psi of each other, vacuum gauge was pretty steady at around 20 in/mercurcury. This went on for months....finally, I pulled the inlet manifold and plugged the heat risers on each side. Put it back together; viola!! what a beautiful thing!! The heat riser passage inside the manifold had obviously blown out, as the engine heated up, the crack would open up and contaminate the incoming fuel /air charge.
I dunno if this is your problem Craig, its way out left field, but why not pull the manifold, replace the gasket with a generous slathering of grease as I talked about in an earlier post, insert a coupla thin shims over the heat riser passages [which can subsequently be removed if this doesn't cure your problem], tighten it all down and try it?

One of the wonderful things about flathead Fords is their basic simplicity, they are basic, aren't they?, until you experience something like this. Ain't it fun?