18U143390 is the partial VIN of the car it came out of. In this case it's a 1968 full size car built at the Lordstown, Ohio plant. T1229HM is the engine suffix code and this shows the engine was assembled at the Tonawanda, NY engine plant on December 29th, 1967. HM is the engine code, which is a 327/250 with a Turbo 400 and a 4bbl carb.
Ed