Nathan, as a simple try-it-and-see option, you could revert to the main alternative and try to clean up the seat you have. You can do this by using an ordinary deburring/countersinking hand tool, very gently. These devices are cheap and have red plastic handles on a multi-tooth, 90-degree-included-angle countersink. To try this:
1. Set your carburetor up so is stably supported upsidedown.
2. Rest the countersinking tool vertically in the hole in the seat, using a square to make it exactly at right angles to the float bowl top gasket.
3. Rest one fingertip on the top of the handle of the tool, to hold it steady. Do not apply pressure, or you'll wreck the job (and the seat).
4. Rotate the tool by the handle, using two fingers of your other hand, without applying any vertical pressure. Just one turn is enough for the first try.
5. Remove tool, and use a magnifying glass to inspect the seat.
6. Repeat the whole process until you have a smooth, even edge all the way around the inner corner of the seat. The edge should be very narrow - barely visible - but of constant width all the way around. Any chatter marks or lack of squareness to the bore will mean you've wrecked your old seat.
