Engine identification help please

[eMars013]

I have an engine that I strongly suspect is not original installed in my 1976 K10 project truck and I would really like to know if this engine is worth keeping for the long term and overhauling for moderate performance or if it’s a worthless pile of junk. I have included pictures of the numbers stamped on the block as well as what I believe to be the block casting numbers, the block stamp is pretty clear, but the casting numbers are semi-vague. I personally believe the casted numbers say 371 and 388 followed by a 134 N. I can’t figure out what the block casted numbers correlate to. Does anyone have any insight here?

 

[eMars013]

Additionally, I flipped the image of the cast numbers, they appear upside down on the block itself. Don’t know if that matters

 

[eMars013]

alright, for anybody who's been looking at this thread and wondering along with me, I found more numbers on this block. apparently this is a 3970010 block which means it could be a variety of things. further investigation is ongoing

 

[eMars013]

alright gentlemen, I've determined that the heads are 333882 casting number heads. I don't know if anyone has any interest in this anymore as I seem to keep finding more information on my own, but im no closer to determining if this makes sense as the original equipment for this truck. it is in fact a 350 engine but based on the stamped suffix code of CKY this could either be a 255 HP corvette LT1 engine from 1972 or a 145 HP Camaro L65 engine from 1973. (as a side not, this leads me to further believe that this engine is not original to the truck because of the date discrepancy between the heads and the block. the heads are dated 74-80 for this particular style while the block stamp indicates 72-73) obviously the corvette engine would be way cooler, but I think its highly unlikely. the L65 is also a 2 bolt main vice four bolt according to nastyz28.com which would be a bummer and highly considered for replacement instead of refurbishing

 

[eMars013]

alright friends the story gets weirder? aside from the fact that im basically writing this all to myself I mean....
the cast manufacture date on the back of the block (behind distributor just in front of bell house) says K135 which I take to mean = November 13 1975. which is weird given the stamped block numbers pictured above. so now I have no idea what the stamped block numbers mean anymore aside from the fact that this engine was put together in Flint. but on the other hand Nov. 1975 is very period correct for a 1976 chevy k10 equipped with a 350. the only other confusing factor in all this is the fact that the engine block is painted chevy corporate blue. which isn't exactly correct for the year, 1976 was supposed to be the last year engines were painted chevy orange according to several sources I've read. if anybody can put all this data together and turn it into something that makes sense please let me know. My inner idiot can't seem to let this go and just live with the fact that its a 350.