I knew what ya meant.
On a 4WD there's the offset oil cooler adapter with the small filter; on a 2WD it's straight down oil cooler adapter and uses a large filter. The engine may be original but for some reason the adapter was possibly removed? Oh, ya know, leaking lines they got sick of messing with? Or like you're wondering, possibly a replacement engine from a 2WD truck with the other adapter.
Do Evo's use spin-on filters? I've only ever owned Shovels with the drop-in cartridge filter that goes in the oil tank. So the filter difference where they look the same but have different media, that's what, an Evo vs. Twin Cam thing?
Richard