I have gotten a couple old tractor motors freed up from pouring diesel fuel into the cylinders and letting it sit for awhile an then just try jerking it loose.
if has siezed from setting you might try pouring trans fluid in through the spark plug holes and letting it soak in overnight then try rocking the crank shaft back and fourth. more than likely it will have to be completly rebuilt
Drop-in a rebuilt short block.
Rip it out & drop another in. Other than originality, not worth fixing.
It has set about 9 years
