If you are going to replace the tank, Johnson models J-75, J-80, 100 and 110’s all used the same 12-118 tank while models J-25, J-65, J-70, J-75 and J-80 shared the same 12-53 muffler. For the condenser/capacitor, the original 72-13 cap was rated at 0.13 uF. A modern Vishay cap with a rating of 0.10 uF could be used if yours tests bad.
Those part numbers are long obsolete but this should help you narrow down your search for parts. Doug Penn might be worth a try as he has lots of parts and reproduction grips. ☺
Here’s some pics of a J-75 I found somewhere to help you see what your muffler looked like originally. Notice the short tiller with what might be a bicycle grip on it. The tanks filler is also in a different position.
