As you have by now probably realized, the hard part of converting the Poulan 46cc is dealing with the carb mounting situation. Once done though, it does make a quite nice conversion engine. This engine was the base for the (now defunct) Brilleli 46cc, and he did a very nice job on them.
For some hints on dealing with the carb mounting problem, see the old "rcfaq" website, plus have a look at my "Stihl 62cc" thread in this forum. (The Stihl is easier though, as the port is round instead of oval, and has more "meat" to work with.)
Whatever the solution you come up with, don't neglect the necessity of having the carb AND carb mounting screws thermally isolated from the engine. Not doing so will lead to incredibly frustrating tuning and operational hassles. (Yes, ask me how I know....)
It might seem arcane or silly, but using epoxy soaked plywood of good quality can be a viable part of a carb mounting setup. Diluting the epoxy with acetone helps the epoxy penetrate the wood. (I prefer acetone over alcohol for this as it evaporates faster and allows the epoxy to cure completely faster.) Another good option is the material called "G-10". Try McMaster Carr for that. (A bit pricey.)
Good luck with it and keep us posted,
AV8TOR