It might not be as bad as you think...
The other year, I bought a 1930 A engine that previous owner had pulled from a Doodlebug, then stuck in in an open, wooden shed for 25 years. supposedly, the engine ran when it was taken out of the 'bug.
When I found it, it was stuck. I went ahead and bought it any way, as it had teh ****** too, and I figured I could recoup my investment in parts or scrap if it was junk as an engine.
When I say this engine saw some weathering, about half the cylinder head nuts were so badly eroded, they not longer had flats on them !
The spark plugs ( what was left of them ) were "take-apart" Champions, two of them had no nuts left from the upper "clamp ring" that holds the porcelain in the shell.
I put it on the side, in the shop, right-side up, pulled the plugs, and kept adding Marvel Mystery Oil to the cylinders, a few ozs every month.
After a few months, it finally loosened-up.
So, I decided to dig into it, and see what it looked inside.
The very eroded nuts were fitted with the nearest size six-point metric or SAE scoket.
The head nuts all removed nicely, and even the distributor too... and the head came-off rather easily, after rapping gently on all four edges with a 3# dead-blow hammer from Harbor Freight, then gently working a putty-knife, then a screwdrive between the block and head.
The head came-off with nothing more than my two hands and some patience.
You might be as lucky.
As for "what I found inside", so far I have found a lot of carbon, a deck with no cracks, and original (standard bore) Ford pistons and original Ford valves. So, then most work this engine probably saw was a valve-grind and maybe a re-ring, if that.
I still have to flip it and check-out the bottom-end.
Good luck with your project !
SC Frank