1987 honda civic - oil in radiator

after having broken timing belt fixed, head rebuilt, axles replaced and now
the latest. Me and friend needed to replace the pcv valve and when we
finally found it, it took us quite a while and we replaced the oil pan
gasket in the process. We then noticed a leak, just a few drops. In
checking it out, it appears to be oil in my radiator. I drove the car
home and checked the trans and the oil, neither appear to have water in
them. The only reason I checked the trans was, I am use to the old cars
with automatics having the trans lines running through the bottom of the
radiator. Does anyone have any idea why and how oil could get into the
radiator. Pleassssse help, thank you