If the block casting number is really 3877178, it is a 230/250 block. The year range for that block depends the the source of info, and goes from '65 to '78. I think '66-'72 for the 250 is about right.
This engine was originally built on March 9 (0309)at the Flint (F) plant. The TA suffix is for the standard 250 w/ manual trans., 1 bbl. carb., 155 hp, and was used in the '66-'68 C10-20 and K10-20 trucks. The casting date code on the block would pinpoint the exact year.
