well missing the head is never a good thing but i have saved some really bad ones from the melter . is it stuck ? there is the first issue are the valves loose in the guides like flop side to side ? that can be a pain it will burn oil like a foger if there gone to far hows the cylinder? if thats all scored to hell your looking at needing to do a hone or bore over .
whats the guts look like , cranks rods and all that are easy to fix . bearings not so much bit more work to rebush a block . but ya i would say its worth a look to save it .
for fun a few years back i got a 1961 3 hp i think it was . stuck tight as a drum full to the mark with water in the case . took me 3 days to get it apart using a pipe wrench to turn the crank and some fire in the bore . but it did come apart cleaned it up swapped the crank and cam for some less trashed ones different piston from a parts block . got great compression and spark but havent got it to run . wrong flywheel on there is my guess . but it should go with a little more work . so check yours out it maybe a good block with a little help , or spare parts to get the next one going :hammer::grind: