Hey Nate. I know little about the DuraSpark but let me share my ignition history... I too just dropped a hot 390 into my 65 F100. I grabbed a DuraSpark distributor and coil out of the bone yard. Instead of using the DSII box, I went with the GM HEI module and wired it in. So far, I too have about 100 miles on the truck (around the neighbor hood a few times..) and have not had problem uno. If you want to give it a try, I can dig up the thread from here.

Just a few $.01's (that's all I have left) --Mike