Mate you have very high expections of a 40 year old, carburettored design.
Only now are modern hybrids and ultra-efficient diesels edging towards the 6 litre/hundred mark.
By comparison, my mothers 1995 kj 1.6litre laser gets 9litres/hundred, and that's with EFI, DOHC, and all other shit they put on cars these days.
I don't think automatics do anything to lessen fuel consumption but with the figures you're getting, I don't think you have much to complain about.