Not sure why I have not seen these posts to respond before now but sorry here goes,
Jr. Dragster tach yes they will work, must diode isolate them. If using the billet wheel and briggs coils its working off the briggs ignition, but will work on the indian also.
Yea the digatron stuff is easy and simply the best investment I have made. And I love looking at each lap on the puter and seeing what I did.