I'm looking at your motor from 1000 miles away and can't see any flaws lol. Factory spec says up to .007 cylinder taper is ok. If the pistons aren't broken and the cylinders don't need truing hone the cylinders with a bottle brush hone, put some new rings on and run it. Check valves and guides for wear. Lap the valves and shim the springs .060 or, you may want to replace the springs if you are adding a cam. Timing chain, oil pump, bearings, crank will need to be checked. But the bore job suggests the engine has been rebuilt once and not run a lot since them. I think it looks promising but you never know until you take it apart and inspect. I lean towards putting in new rings even if the old ones are not worn because modern low tension rings are so much better, they reduce friction which is even more important on a long stroke engine than on a new short stroke engine and they practically eliminate wear. If the crank is clean and the bearings aren't worn, I wouldn't even replace the bearings provided they Plastigage to the right clearance. With a little luck you should be able to freshen it up for the cost of gaskets, rings, maybe a timing chain. Might cost under $500. And, you already have the carbs, intake, etc off your old motor. I don't see a down side to using this engine. Even if the crank needs turned that might add 2 or 3 hundred to the cost. But, you would have practically a rebuilt engine and it will drop right in with no modifications. I severely doubt you could rebuild a slant six and put it in for anywhere near the same cost in $$$$ and labor.