Put a hone on it and see where it cleans. Do the worst cyl. first. Piston mfgrs. will make you any odd size pistons, so too, Total Seal will make u any size rings. My 1265 hp bbc blown boat motor (bowtie block, max recomended bore 4.5") had 4.614" pistons in it for the last 10 years of my owning it, the purchaser is still running it after buying it 6 yrs. ago.
Once u know what u have, offer it for sale here, I bet it will sell to someone that will block rock it and use it for a drag only motor.
I have done my share of using worn out blocks, filling them to about 1 and a half inches below the deck surface, and setting records in the process. The "fire" is out in the first inch of piston travel, so, not a big deal.
Filled, it would also make a great dyno mule for testing, or backup use.
We regularly bore BBChevies .125 and .140 over for street/strip use without filling them. I have done two at .220 over! Check strength of metals vs. length on google before u trash it!
I did a science project in Jr. High using round 1/4" solid glass rods. Took a 1 foot free length between 2 supports, added suspended weight from the center until it broke. Then took a 6" then 3" piece and did the same. The results will surprise you!
Smokey says .100 on the thrust side works for SBChevies, but that depends on unsupported cylinder length.
I have a sonic tester, so I can use what others discard. Done a LOT of it in the last 50 yrs of business.
Your $$$$$
Your call......
TIMINATOR