Probably not related here but some of the 350 Olds Diesels used in Motorhomes etc had a remote oil cooler option, extra plumbing to and from the oil filter adaptor. I think it was also a rare option for some of the Olds A bodies with towing option, I guess the auto lines may have already been plumbed on the engine side. Who knows. I haven't seen this type in a Firebird, regardless of engine etc. Not sure if there's any stamped codes etc on the radiator tab half way down. Very interesting. I always imagine the more things that are plumbed to a single radiator, the cooler they run, but also the harder it is to cool each of them combined!
Do you know what the 350 came out of originally? If not, the start of the engine number tells you year and where built which often equates to certain models. Could even have a peek at oil filter and see if standard adaptor with no plumbing, just in case pulled from same vehicle. Just ideas, still guessing.
