The car is an 84, is the "86" something different or is this motor a later casting? As the oil pan is RTV'ed and so is the front cover, this thing was apart at some point so I am wondering what year motor it is.
The 86 does appear to be the casting year. I've had '767 casting heads that have read, 84, 85, and 86. I was looking at one last week that read 85 that came out of an 85 motor.
It's entirely possible that the head is newer than the rest of the engine.
To tell if you've got a 85-86 block, you can look at the lifter cover on the side of the block. The bottom corners of the lifter cover will have a chamfer, whereas the top will be plain corners. There are also two "dimples" poking out of the cover in the middle (left to right) that are above the height of the cover studs.
If you're tearing that down due to cracked head, the '373 casting is a direct swap, FYI, and no it doesn't flow any better.
'552 is supposed to (it doesn't have the severe "swirl port" obstruction, but I haven't had one on my flowbench to confirm, since they were only used on VIN R until 1983. I think they may also have a larger chamber volume, so compression could suffer.
I tore it down because someone wanted to buy the head. The cam gear sheared off like they do, so the block is going to become a table. Take a guess which cylinder didn't have a plug in it for 6 years?
I dunno if the head is savable, but I told him I wanted $30 for it.
84's that had the engine replaced under warranty got an 86 casting motor, but made in 88. My 84 was like that, it had the roller cam, but also had the 88 crank with the gear in the middle for the oil pump.