Harrison oil coolers were used on several early Camaro Trans-Am cars, and were available over the counter at GM dealerships. Well, these oil coolers were also used on many other GM race cars, including Corvette Grand Sports, many of the Can-Am competitors, Formula 5000 cars, and on numerous non-GM cars and engines as well.
The GM part number seen and quoted most often for the Harrison oil cooler of choice is 3157804. Much of the "How to Hotrod" manuals and other sources from the late '60s and early '70s note something to the effect of them not being ready to use as is. They further specify that these coolers need to be cut apart and modified so that the oil flows into one end of the cooler and out the other.
The first pic attached shows a 1978 dated, 3157804 oil cooler that I have. It flows from one end to the other. From the plating wash that exists on the whole unit, it would seem that it came this way new. If it didn't, someone took the time to dip/plate it as per original after the modifications.
The second pic attached shows quite a lot of original Harrison oil coolers, mounting brackets and other hardware that were offered on an eBay auction several years ago. Note the various ends and fitting provisions on these 3157804 oil coolers.
Does anyone know if Harrison/GM ever offered these oil coolers with the flow (and fitting provisions) going from end to end?