Ideally 172.5mm, however I've just found a NOS double 175mm on ebay in the U.S for £60 so have ordered that (all my bikes use either 172.5 or 175mm). Now I'm just left needing:
braze on front mech,
109.5mm octalink bb,
12-25 cassette (I already have a 6500 11-21 here but it's seen a few miles)
I'm picking most of those bits up later this week from another guy also called Tony on LFGSS so I could well be sorted for this project. However I'd be interested if you have any of those parts yourself and prices etc.
Am also keen to get my hands on a 7400 8spd rear mech (medium cage if they exist), cash waiting.
I just started using old 7400 STIs with a old 105 rear mech on my 1x8 hack bike and realised I've been stuck in a campagnolo mindset for too long. I might well go with a DA group for my next forthcoming project and am open to the idea of a triple set so interested in what's available.
If you don't mind when you have time PM me some pics and prices of what you have.
Thanks for info on Shimano double/triple compatability issues, with campag I always seem to get all kinds of odd combinations working. I've even got a Sram, Sunrace, Campagnolo, Shimano & Miche bike setup currently!!!
It looks like things are taking shape but I'm still interested in whatever you have available, thanks.