hmm.
well, there was no 440 T Jet in '74, it was 340 only that year i believe.
i talked to an old Yamaha racer today. he told me a few of the yamaha race teams hand built some of their own pipes durring mid season back in the day as the stock yami/TJet GYT pipes were not that great...especialy in '74
i am sending him a pic to positivly identify them (hopefully). he thinks they are a rare custom set of race pipes.
these pipes are not stamped, they are welded.
the quest goes on............
thanks for all the info guys.