old D8-12a cat. runs good but in need of help

Just bought this machine.Runs great but I popped the radiator cap and its all dark oil.No signs of antifreeze.I heard the oil cooler can leak.My question is do these old timers even have oil coolers,and if so where are they?In the radiator core or external?There is no anitfreeze in the oil that I see.The macine is in great condition and was purchsed cheap so Im going to fix it as long as its not a cracked a head.I have some oil coming out of one of the seals in the exhaust also.Not looking...

old D8-12a cat. runs good but in need of help

old D8-12a cat. runs good but in need of help