Cooling system leak

[Hole$shot]

I have a 67 Firebird with an engine that was recently rebuilt. On hot days, the car isn't necessarily overheating, but I am noticing coolant gathering between the water pump and the block. I can do a pressure test, but I'm wondering if there is another way. I thought the leaks were coming from the sensors in the manifold (Edelbrock Performer), but it doesn't appear to be that. I am left with the Radiator "in" (which is tight), the junction between the water pump and manifold (which I hope isn't the problem, because removing the manifold isn't fun) or the water pump itself. I have a water overflow bottle that is NOT vented (inlet on bottom) and running a BeCool aluminum radiator. As for timing
I am running 8 degree initial, 34-degree all in by about 2500 Via MSD distributor (this is the best I can do, as I'm using the "Black" weight stop and the heaviest springs). Could it be that the overflow bottle should be vented? Would that release pressure?

 

[melsg5]

trying to first understand what you have radiator/overflow bottle wise. Does the radiator have a conventional neck with a radiator cap? If it does, what pressure cap are you using and is the cap a sealed cap, a rubber ring around the outter edge of the underside of the cap? If you have an overflow tank of any kind it has to be vented. If you have an expansion tank they have their own cap. It might be easier if you provide the part numbers of the radiator and tank so I can see what you have.
Did you install the intake? If you did, did you snug up the long bolt that goes between the intake and water pump before tightening the rest of the intake bolts? If you did not do it in that sequence there is a good chance the leak is between the intake and pump.