['68OrangeSunshine]

F0219UH.
Flint, Michigan
02 = February
19 = 19th
UH = 292 L6 w/manual trans '67,'68.
Sweet block.
I have one 292 I ran from Summer 1977 to Fall 2002. F0626UH. Came out of a '67 K/20 Forest Service long stepside. Laying fallow now after a 250,000 mile run. UH blocks predate the "1970" casting number. It's not a date code, but I've heard people claim their '68 truck has a '70 motor because of it.
The engine that was in my '68 C/10 when I bought it in June 1973, was F0627XAE. [To date no one has been able to decode "XAE.''] After a performance rebuild, that block is back in my Stepside.

Those tubes in the head were for the A.I.R. [Air Injection Reaction?] smog pump.
A belt-driven smog pump on the passenger side, sucked exhaust fumes from the exhaust manifold and pumped them back into the cylinders for a 're-burn' to cut down excess hydrocarbons. This assumed the average driver/owner did not keep the timing and ignition components in top condition. A well tuned engine will burn better and cleaner without that junk. Led to vapor lock and overheating from my experience.
But at least GM could pretend it was doing "something'' toward Cleaner Air.
They should be extracted and plugged. Whether they ever did any good for performance is a debatable subject. My own opinion is they were a political solution to a political problem. I ditched the A.I.R. system as soon as I left California.