1971 slant six 225 no spark or weak spark at plugs?

Thanks. I've never had this issue, so it was frustrating trying to figure it out. Thanks for advice everyone.

Now my stock radiator is leaking pretty steady from the tubes where they meet the tank up top. Enough to lose almost 3 cups or so overnight, faster while engine is running running. I'm considering trying a radiator seal, but as I just cleaned out the block and put a new water pump on, I'm nervous to put an additive in that may clog something up and not even fix the radiator. Annoying because I really wanted to keep the radiator stock