There is a cone-shaped sintered bronze filter behind the fitting where the gas line attaches to the carburetor. They're notorious for getting clogged up and causing exactly the symptom you're describing, and that's something that hasn't changed for the almost 60 years I've been fixing vehicles. I believe the big nut that's visible in the third picture on the top line has 1" diameter wrench flats. Remove that nut and you'll find the bronze filter right behind it. There's a small nylon gasket attached to the nut- - - -put a new one on when you change the filter, and be careful how tight you snug the nut. Too much force will strip the threads in the carburetor and then you'll be looking for another carb.
The "grunt" on a hot start is caused by worn starter brushes. Invest in a good quality rebuilt starter, as 30-something years of faithful operation means the rest of the starter is also worn out. Don't waste time and effort putting new brushes into a worn out starter.
Jerry
