Unless the VIN on the side of your block can be matched to the actual 'real' 70 440+6 GTX VIN its "he said she said" Also since he said the 'engine& tranny' came from a 70 GTX 440+6, so the VIN codes on your tranny and engine should match (right!). That will be the first indication on a tall tale or not. Other then matching the original car to your engine VIN the only other tell tale signs of a True six pak engine is (4 valve reliefs on the pistons, External balance,three bolt cam gear). Those numbers/letters on that engine pad in front of the intake won't tell you anything about a six pak engine other then its build date/year. 'F' is a 1970 build year. Regular 440 Hp engines came with 1 bolt cam gears. There are regular externally balanced 440HP engines so external balancing won't guarranty a six pak engine. This was all covered in the above posts.