Originally Posted by
fietsbob
'Ultegra' bar end was the 8 speed, 'dura ace' detents closer together for 9 other than that, no quality difference .
You may be facing an incompatible parts & frame mix for your wished for modernizing outcome..
so tapping and filing is in your future, & maybe a 9 vs an 8 cog cassette.....
I would agree that the claw approach isn't the right one for this application.
For one thing, the derailer is going to have to move inward to it's very limits of travel just to reach the largest cog, which may affect indexing accuracy in the range of the largest cogs.
Another issue is that the quick-release will need to be made hugely off center, using a much longer spring on the right than on the left.
Either that or no springs.
As far as the shifter, if it is actually Dura-Ace and with only 8 actual indexing positions, then it is designed for use with the 740X type of derailer (or a standard derailer with modified cable anchoring, which is somewhat trial/error in terms of the exact cable routing placement).
A Suntour XC Pro 8s rear derailer will also index reasonably well with 8s Dura-Ace shifters and could very likely handle your choice of gearing, though the later ones were intended for use with MicroDrive-sized sprockets.
If I were doing this I might start by trying
whatever Suntour Accushift MTB derailer that I or the co-op had laying around.
Likely the 7s versions (more common, inexpensive, and made for non-compact sprocket sizes) can span Shimano 8s, so I think it is worth trying. This won't work with the claw!
Note that Suntour 3040 or any 3XXX series Accushift derailers will not work here, they are the cheaper/heavier ones and had their own indexing standard using a longer cable travel.