M_V's multitude of bikes and adventures in the land of framebuilding

I have is 8speed whereas my bar end shifter is 7/friction, I'll use it in friction mode at first but indexed gears might be on the horizon at some point.

If the bar end shifter are indexed for Shimano 7 speed, then the spacing is identical to the 8 speed, bar one cog.

What you can do, is take off one cog and run a spacer between the hub and cassette to run a 7 speed indexed set-up.