Hi BJ, I guess I'm a little late joining in, but I found what helps in filling a dry 1500 cooling system is to take the upper hose of the heater box off (that's the big black box in front of the battery), and that burps out most of the air pocket. Without doing that you might have a lot of air trapped in the block.
Another thing I'd pass along since mine was pretty rusty when I got it is that the heater return pipe can clog easily, leading to some strange symptoms. The automatic choke's water jacket and the heater both connect to a T fitting at the rear of the engine block, and that T is attached to a pipe on the right side of the engine which leads to the water pump. If you get enough rusty sludge like mine did, that T can clog up, and the choke won't work right at all because it won't get any heat. A coat hanger wire can clear out the tube, but thought I'd mention it too.