Couple more hints:
Yes if your plastic blocks on the 4 screw or 3 screw pump are sealed good just fix the front pump area so as a cheap Briggs type pulse pump can be installed using the existing pulse hose, let it pump through the old pump body. I usually just do the gravity flow run test mentioned previously to see if a unknown engine is any good.
Also when you first start testing you can either just remove the large carb bowl drain plug to see it pumping and spilling gas past the inlet needle and float and if not seeing gas you can lift the top of the carb off with the gasket at same time and see the gas inlet BEFORE the needle. I use a light grease on the top carb gasket (both sides) when going back so as to get a easy release next time the top of the carb is removed.
You really have to be careful with them old plastic pump blocks, especially the 4 screw. If you crack the plastic body you are sol.
I've never paid any attention to drilling a tapping the front of the 3 or 4 screw carb body for installing a hose barb so as to completely bypass the carb's pump input direct to the needle inlet, because I have a bucket full of old 3 screw carb's that I've saved over the years but my 4 screw carb's and pumps are weak.
On same subject of bypassing the carb fuel pump on the front of the carb's, Kinda costly but some of the old Onan B43/B48 carbs have a obselete pump on their front and guys rig them for bypass/pump through and use a $40-60, 1/2 lb psi 12v fuel pump for their cherished little tractors. They like 12v pump because they can just switch on the 12v at first without cranking the engine and get a direct prime to the carb vs a long crank time for a pulse pump if the tractor has been at rest for long time. Them replacement onan engine carbs are very costly if found and usually VINTAGE. (junk)
and about 3 different types carbs for the B43's with different bolt patterns and require a different air filter.
Kits and things getting out of sight on prices and prices changing daily/weekly and China made.
I'm starting to watch the fuel mileage little bit closer on my lawn mowers nowdays.
I'm suspecting somone is sending us a hint and wants us to convert to the non-polluting battery only equipment.