I prefer Kroil to unstick engines with rings frozen to the cylinder walls, etc.

www.kanolabs.com

Kroil won't repair rust pits, but it penetrates better than any other oil such as WD-40, PB Blaster, etc. Once you get the engine turning, you can do a good inspection of the cylinder walls for any possible serious rust damage.

If the block is welded on the outside, no big problem, even if there's a little weld porosity that causes a coolant seep leak. Use Marine-Tex sealer to cover the weld and stop the leak, after grinding the surface around the weld smooth for an inch or more in all directions. Internal welds that might allow coolant to get into the crankcase- - - -sort of risky to try to use those blocks!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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