Da-Burb is correct that the dress numbers stamped in the pad can tell you what day the engine was originally assembled on. There are also casting numbers above the dipstick that can tell you what day month and year the block was cast. Examples: known '67 292 L6 block --casting #s [CON2 F 22 7] = (CON)veyor line 2, (F)June (22)nd 196(7); dress #s [FO 626 UH] = Flint Michigan, June 26th /not sure what engine codes UH meant, but the LMC catalog lists UH as being on 292s made in '67 and '68. Color may be another clue, I'm not sure what year Chevy Engine Orange came in for L6s, but the first 292s in '63 were apple green, a carryover from the 261s they replaced. Of course a zealous rebuilder could've sprayed a rebuilt engine any color he had a lot of, like orange. Another clue may be the PCV valve line into the carb, early smog gear, which came on line in 1967. Also interesting air cleaner set-up. Is that an oil-bath air cleaner? I think those went out of fashion after '67. [But I could be wrong.]
You can run those numbers on the Inliners International board to learn more about the engine. There is also a casting number after the Conveyor numbers, like 363xxxx that can also be cross referenced.
www.inliners.org
My guess is it's a '67 250 L6.