cant say for sure but I think if used carefully the booster should work ok on 6V systems. I'm sure others will give more advice.
As for the "old" dwell tach, if "old" doesnt equate to readouts that cant be trusted I would say OK. A dwell tach is valuble when working with point type distributors, tuning carburators, etc. Might be an idea to price a "new" dwell tach first. May find the cost for "new" is worth more than the saving buying "old".
good New Year to you too...
Carl
