I've never seen a filter used before the fuel pump and those Pierburg pumps last an awful long time; on the order of 20 years without any pre-filter.

The best test of the fuel starvation syndrome you theorize is a hard sustained acceleration, like hitting the freeway onramp and accelerating toward 80 mph. If the float bowl is going dry, the gasping for fuel will happen every time without fail.

You say you rebuilt the carb (a Stromberg I presume). Did you check the float adjustment? It is possible the fuel level in the float bowl is low due to the float valve shutoff being set at too low a level and this would aggravate the fuel starvation syndrome.

But first do the hard acceleration test a few times to get a clear 'feel' for the problem, then get rid of the pre-filter and repeat the test to see if it makes a difference.

Now I assume that the fuel filters are new. If not, that would be the first thing to change. They are cheap and generic.