For the carb link: The carbs that have the built in primer bulb like that can be easily changed to the type without. There is just one hole you have to plug after you remove the primer bulb. Then you can install a regular flate plate regulator cover on the carb. I use JB Weld to plug the hole, but you could drill and tap it for a small set screw in case you ever wanted to change back. This is important for those who are running completely cowled engines, as then you can solder a brass tube in the regulator cover, and run a hose outside or into the fuselage to reference static pressure instead of the ram pressure inside the cowl.

Mike, if you go to the walbro.com website, you can find carbs and their venturi sizes. From the home page click on "Service & After Market". Then click on "After Market Parts & Service". Then it gets a little weird. It won't show the venturi size at first when you find a carb you want to check out. But if you click on the number of the carb you have selected in the box of parts listing on the right, it will open another window with just the carb and it's price. Above that click on "Detail", and it will open another parts listing box, but this time it will show the carb venturi size.

Hope that makes sense,
AV8TOR