Tear it down?
Nonsense. #1 Pull the plugs. #2 Put a torque wrench on the crank and measure abnormalities in the rotational torque. #3 Pull the dizzy and intermediate, use a drill and shaft to prime the oil pump. Check for oil to the heads while rotating and measure oil pressure. #4 TDC each cylinder and do a leak-down. #5, bolt a bell and starter to it and do a cranking compression test on all cylinders. Use a borescope for lookin inside the holes. #6 pull the pan and valley tray for visual inspection. Pull a rod and main cap if you must. Look for heat marks, loose parts, etc. #7 If all is well put it back together and stuff it.

Whomever built it didn't go cheap. Indy heads and rockers (those don't look like HS), BHJ dampner, ARP, Milidon, Edelbrock, MP covers, etc. Mid-level standard stuff for many today, but this thing was built...what? 20 years ago? You have the receipts,

You tear it down and now it's off to the machine shop, new parts, upgrades, and more time and money. Inspect it like you would any used car and run it like you stole, because for the price it's practically a steal.