I’ve just finished a cb550 street tracker style build.
I used a motogadget pro speedo / information unit.
I initially thought about mounting the supplied speedo magnet / pick up on the engine sprocket but decided there was not enough room.
I decided to mount it on the front wheel and the picture shows where I mounted it.
I put the magnet in the edge of the disc that I had drilled to give a modern look.
After drilling the edge and glueing the 4 mm magnet in the hole I routed the cable alongside the brake hose.
After fitting I read that magnets may stop working at temperature’s over 100c.
I’ve since done 500 miles on the bike with no problems so think it’ll be ok.
Hope this helps others that may be looking for a pick up location.