Before you spend a dime on carb kits, coils, ect. You need to do a compression test on all 4 cylinders.
It probably does need a fuel system overhaul and some ignition/charging system work, but there's also a good chance that your 1979 140 has some sticky rings or cylinder damage.
Always check compression first, then ignition system, then fuel system... whenever diagnosing engine running problems
Where are you located ?