Oil in the rad

I have a 1993 Mazda B2200, 2.2L, 4 cylinder fuel injected with about 80,000 miles.
Recently I noticed oil in my rad but no coolant in my oil, a few days later I started noticing coolant in my oil. I thought 'head gasket' so I replaced it and the intake manifold gasket. When I took the head off the pistons were dirty not washed out like they should have been. I am loosing a great deal more coolant than what is showing up in the oil. The engine doesn't blow white smoke and I am not loosing any motor oil, so that should rule out a cracked block. There is no visablle coolant loss.
I am at a loss for this problem and need some new ideas on where to look