Love these old cars, more often than not a simple and cheap fix!
Inline filters exhibit poor acceleration & lack of full power when block/ed/ing.If there's a filter in line, should be easy to figure out if there's crap coming from the tank or not. Depends also what type of filter you have. A paper filter is not likely to let anything that could block the jets through, whereas a mesh one might.
And is there a mesh filter in the tank at the end of the pipe to the pump?Fuel pump will also be probably full of rubbish.