Typical of most Chevy parts, the intake will have a casting date on top in front of the distributor; the heads will have casting #s and dates and so will the block. The block should also have an assembly date stamp and suffix code for it's original application. The 348-409 site is a good source to look up those numbers.
BTW, no 409 was ever produced with tri-power, although it could easily by installed on any engine with the small port heads.
Verne
