Rev counter drive b50

[Dave Halsall]

Morning all.
I have  a 1971/72 oil in frame  B50 it's come  with  a rev counter  drive  which  l would  like  fit . It appears  to be of the early type. Apparently  there  is a later  type produced as well.
Can I fit this early  type  rev counter drive? 
I gather  the early  type cable  entry can possibly  foul the frame but  looking  at a later  type there doesn't  look at to be much  difference.
Any  help  will be most appreciated.
Happy New year to  all

[Rupert]

With the earlier type tacho drive the frame doesn't allow for easy routing of the cable next to where the cable end nut screws onto the drive. Maybe try it and see? - but I've seen several early tacho drives with a broken thread resulting from doing that. The '72 type drive allows the cable to start bending around the frame nearer to the engine - it works fine.