'69 Mustang in the workshop

I've known this car for 3 or 4 years now, the last time it came in it had snapped the oil pump drive shaft, fortunately without causing any damage as it was stopped right away. The owner is concerned about coolant loss, it coughs every now and again and spits a cloud out of the right side tail pipe and the last time he changed the oil there was a little water came out first when removing the drain plug. As this oil change has just been done I will crack the sump plug and see if any more water is in there, I'll also put a little pressure in the system and see if it holds. It's also apparently leaking transmission fluid from the shifter shaft seal, it's a common failure point, and just about the only place in the transmission case that can spring a leak.