My understanding is that Dura Ace 7400 was offered as just as 7400 (maybe as FH-7400 for a 6/7 freewheel), FH7400-6 (6 speed freehub/cassette), and FH-7400-7 (7 speed freehub/cassette). There were also a couple of 8 speed versions, but the OLD of those are probably 130mm.
Depending of whether you want this to be a rider or wall hanger, the 7 speed Uniglide cassettes for Dura Ace had a smaller diameter threaded 1st position cog. Same goes for Dura Ace freewheels.
If you go with a 7400, for a freewheel, you can run any 7 speed freewheel, even newer Hyperglide. An older Shimano Uniglide, Suntour, or Sachs Aris are good choices, but nothing is cheap these days.
I ran a 13-28 Dura Ace 7 speed freewheel and swapped out the 23-26 with 24-28 Uniglide cogs. Even though the 28t exceeded the max cog for an RD-7400, it was fine for me. But YMMV.
John
Last edited by 70sSanO; 11-14-23 at 07:33 PM.