Not sure how many will spank me, but I’ve done on several SBC’s as a kid the same thing Tubman said. Most were junked engines I bought on the cheap in an emergency to get transportation back on the road. Having said that all the engines I bought that way I checked they weren’t seized flooding cylinders w a cocktail of oil, liquid wrench, CRC, Marvel & what ever else I had before trying to turn w big Wrench. If they turned I let marinate a few drained all, put new oil, plugs, wires, Dist cap points condenser & I can’t think of one that didn’t fire up. Most smoked a bit for a few weeks but cleared up!
Having said that, the rust I see in ur pic’s is less than I’ve gone w in SBC’s my only experience here, as I’m still on my 1st Flatty for last 12 yrs. Previously a GM OHV guy. JMHO but I’d of juiced up all the cylinders w afore mentioned cocktail & let marinate a few days & turned w a wrench before removing heads or manifold. If it turned as Tubman said I would’ve made sure plugs, wires & ignition was OK & cranked it up. My bet is if it ran before it would start, smoke for a while then as Mike in Mass’s Dad said miles of smiles, or worse case then disassemble & refresh what needs replacing which is kinda what ur deciding now anyway. Again JMHO