Did you loosen the carb cinch bolt? If not, loosen it, then gently wiggle/twist the carb and it should let go so you can take it off and put it back on in the direction you need. Just make sure to push down on it hard once you get it where you want it and hold it while tightening the cinch bolt back up.
To get the clutch off the old engine, just slide the shoes off the pins and keep in mind that the springs will want to pop out on you. Then grab the flywheel in a pair of channel locks (use a rag around the flywheel to avoid marring it badly) then remove the flywheel nut. A typical 4 way glow plug wrench usually has a nut driver on it that fits.
Then, tap on the back of the flywheel with a screwdriver handle to break it loose. Reverse the process to put it back onto the new engine.