If this is the problem, then the chain would wear into the water pump cavity, at the top of the timing chain cover. If you do not have the two parellel grooves, as shown in the above pics, then my next guess would be a crack in the block, or head. these are the only two other places, if I remember right, that the oil and water are close enough to pass.
Also, are you getting any oil droplets in the coolant? If not, then the water is passing into the oil return passages. ( going into the valve cover, oil drain passage, timing chain cover, or oil pan[bottom side of block]) A good idea would be to drain the oil, remove the valve cover, and fill and pressurize the coolant system. You can do this with the pump-style coolant system tester. While it is pressurized, inspect all of the areas I mentioned for any spray, drips, etc.
If you ARE getting oil in the coolant, then the transfer is happening between the water jacket and the PRESSURE side of the oil passages. (inside the head) if this is the case, and you pressurize the water jacket, you should see water coming out of the bearings of the camshaft, rocker arms.
PS, Leave the oil plug out until testing is complete, this will let you know when the water is actually going into the oil pan.
