"Get a cooling system pressure test and a compression test for the head gasket to diagnose where the oil leak is occurring (either in the head gasket or the transmission cooler in the radiator). Get it fixed ASAP before you lose either the engine or the transmission."
I would agree that testing has to be done--but be cautious about the procedures--you don't want to make things worse. Take a compression test first--that may set you in the right direction if the gasket is blown in such a way that compression is being lost. A pressure test on the cooling system may lead to coolant being forced where you don't want it. I'd disconnect the trans cooling lines at the radiator first--pressure from the trans oil may be forcing its way into the coolant -- but you do not want it to go the other way. If the radiator trans cooler section is faulty you may see pressure being lost out the cooler fittings. If the frothy mixture is motor oil there may not be a clean way to tell--the headgasket may be blown or the head surface eroded in the area of the oil transfer between the block and head and putting pressure into the cooling system may force coolant into the motor oil system.
If you should find it to be a radiator problem--I have 4 of them sitting around waiting for new homes--they're all good--both plastic/aluminum and all metal--they are the type that fit all 240 and early 740----$20 cheap. -- Dave