273 Engine will not start - Ideas?

When you used the spark tester at the coil did you just pull out the coil to dist. wire and put in between the coil and the spark plug wire to the dist. ? I am having issue somewhat like you had.
Yes, I stuck the tester directly into the coil in order to eliminate any possible issues. I had to make an adapter to be able to use it in the coil. The new coil had absolutely no spark. I disconnected the battery and distributor wires and reattached the old original coil and did the same exact test and had plenty of spark.