I tore the engine totally down, using heat to loosen many bolts.  I did break 2 studs off, but was able to eventually remove them.  I took the cylinders and heads into Red Rooster and had Jerry Frost sandblast the rust off, replace value guides, replace the 4 exhaust valves, and grind the valves.  All 8 value seats were usable.  I honed all cylinders, but number 4 was scored more that the others.  I had to replace number 4 piston due to overheat wearing cause by a mouse nest.  The carburetor was totally frozen, but heat again proved to be a great aid taking it apart.