I know that they made improvements to the dog house as they went. If you remove the glove box, there should be a way to pull the carpet sourronding the dog house as a single unit, at least that was possible in the late 70's early 80's modles. Then ther is a plate held on with approx. 16 bolts. With this plate off you should be able to lay on top of the engine to remove belts or the water pump. When I did it, alongside the road no less, I took the 4 bolts off the fan where it mounts to the water pump and set the fan and clutch in the shroud to place it out of the way. Then I could pull the pump. Of course my radiator is tall and yours is wide
On my 78 if I need to do it, I shouldn't as I have a new pump on my new motor, I think I could do it from the top.