The 5.0 and 5.5 Engines are nearly identical, small difference in displacement, the carb bores are probably nearly identical as well, with different jets...
I used to do alot of experimenting with carbs...
I ran a 13hp honda carb on an 11hp honda, 9hp honda, and 8hp honda with only a jet change, ran perfect. I adapted a 13hp honda carb to fit a 6.5 Honda, I had to modify the governor spring because the carb flowed alot of air at partial throttle and it wanted to rev past 5500, but after some adjustments, it ran great, ton of odd idle power and negligible hesitation.
Im running a 6.5 (OH195) tecumseh carb on my OHH50 tecumseh I just built, starts on 1 pull and idles great, tons of power, Ive got it mated to an 1800psi/3gpm pressure washer pump and it pulls it perfectly, only had to rejet it.
I put a 17hp Briggs rider carb, on a 10hp Generator, ran fine, actually solved a tip-in bog the engine had always had, ran the right speed, idled fine, I used the jet out of the stock 10hp carb, worked great.
On the tecumseh carbs in question, under the primer is a little rim, outside the little rim is an opening to the carb throat, and inside the rim is an opening to the fuel bowl. When you push in the primer (always push smoothly, and hold it for 1 second before releasing), the primer seals against the rim mid push, and forces air into the fuel bowl, which forces fuel up the main jet and Emulsion tube, into the carb throat. When you release the bulb, the seal is undone, and air draws in from the carb throat (or on vented bulbs, through the hole in the bulb), and the process starts over. There are no check valves, its crude but effective.
The system relies heavily on a well sealed fuel bowl, because if pressure cant build up in the bowl, it will not prime, at all..ever.
The bowl vent, is the port behind the primer..dual purpose.