Blue is a nice color, and I think pretty rare, so I would think it would be more valuable to keep it original, especially if it is all original already. Since its a 72, it might not matter as much as a 70 or 71, but I think the 4 speed would add value for sure, unless, again, the car is otherwise all original.
b5 vs b7, I prefer b5, but thats just me.