Is it the press in type or screw in type?
If is the screw in type and notches are not completely destroyed a hollow ground flat blade screwdriver that reaches edge to edge may still be able to remove it. Novices are that don't know it usually use regular flat blade on attempted removals and it simply climbs out of the brass seat notches.
Following is the instructions from the service manual for the press in type.
To remove the pressed-in metal seat:
1. Use a Part #93029 self-threading screw or remove one self-threading screw from Tool
#19069, Flywheel Puller, and clamp head of screw in a vise.
2. Turn carburetor body to thread screw or screw
extractor into seat.
3. Continue turning carburetor body to draw seat out.
4. Leave screw or screw extractor fastened to seat.
Insert new seat from repair kit Part #394682 into carburetor body (seat has chamfer).
NOTE:If engine is equipped with a fuel pump, (as indicated by letter �P� flange marking),
install repair kit Part #394683.
5. Press new seat flush with body using screw/screw extractor and old seat as driver.
6. Use care to ensure seat is pressed flush, and not pressed below body surface or improper float
to float valve contact will occur.
