[OldsCool]

My father in law gave my wife his '66 C10, he has the original in line 6cyl I will put back in it after we rebuild it. I'm cleaning up the crate 350 he bought and put in the 80's, he thinks it was 87 when he bought it new, or 89. Can anyone tell me what these markings mean on the driver rear top of the block? I also show the head markings in case that helps. I'm trying to identify this motor and specs. Thanks

 

[OldsCool]

So this first photo is the upper left bell housing, unless you mean it is on passenger side under the heater core? I can remove the heater core to look if so. I just broke cylinder 1 spark plug and glad I did because they need replaced before I fire up again. The exhaust manifold and shape of this spark plug (short thread flange style) leads me to think this is an older motor than we thought, like a 1969 or 1970 350. Any thoughts on better spark plugs to put in than these AC Delco R44T? That may be original....