Here is how I made the carburetor mount, using a motor bicycle intake tube, and the original tiller carburetor. These are common, and you can test the original carb on your motor for fit by removing it and checking the size of the hole from the back of the carb to about 1 or 2 inches out.
http://motoredbikes.com/album.php?albumid=1441&pictureid=9614 See album "miscellaneous" for more.
Original carb was quite a bit like this:
http://www.quickieparts.com/briggs-and-stratton/images/498298498298.jpg
The gasket for it looks like the one on the right with the round hole. The screws for the carb go in the two holes farthest apart.
This carburetor sucked, because it required a lot of use of the choke to start and did not start easily. Also I think it's governor linkage was overly complicated and it was wasteful of fuel at low speeds.
I used Loctite brand epoxy, that looks like this (it comes with 2 nozzles so you get 2 uses, best epoxy product at the general stores!) :
http://www.loctiteproducts.com/img/products/big/epxy_5min.png
This stuff is incredibly powerful, so use gloves! Beware that it may run also! After gluing the parts, put them over some cardboard or newspaper, and let sit in a cool dark place for 1 day. Then set in a warm windowsill 1 day to fully cure. It will be kind of yellow and very hard when cured.
You can salvage the original filter box and filters if you want, by making a flat plastic plate, drilled for the 2 carburetor filter-mounting screws, and a hole at least as wide as the carb venturi entrance/ intake manifold tube hole, between them. Then place the filter and cover over that and mark for screw holes for the cover, and outline the filter cover to trim the plastic plate down if necessary.