68' M715 stock 230. I have 2 new batteries just repaired the rear main last weekend. Drove the truck for a while yesterday, ran fine. Went to start it this morning and the truck sounds like it has a heavy amp load and the batteries are not giving enough juice. When I check the batteries I have 12.8 volts? but the truck will barely turn over. Any ideas? Tried to start it for 15 seconds or so by then sounds dead. I checked for bad ground and loose connections found nothing so far. I am going to check the spark plugs next. I don't know much about the points and what they do. Any ideas or tips would be greatly appreciated