Take what you got and build it.

[old shed finds]

3 Briggs 3hp blocks take best parts and build one good one.
Here is 3-5 HP Tecumseh fuel tank finishing up the updraft model... Holes on fuel tank bracket line up with Briggs head holes.....

 

[Richard Trotter]

That'll work. good to know the Briggs and Tecumseh tank brackets will interchange.