Got all the accessories stripped off my 1500 single port motor today- there's a pretty sad looking oil cooler under the fan cover...best to replace with a newer, uprated unit or fit an external ?
I'm guessing with the externals the original get's replaced with some sort of a fiiting, oil going out here, through the cooler and back in through the pump cover?
Also there's a small machined slot in the vertical part of the case directly below the original cooler- I'm guessing this is just a breather- or am I missing some crucial bit?
( I've never worked on a vw motor before, so this is all new to me)

give it a really good clean, rinse the inside out with kero (make sure you drain it properly), and then put it back on. If the 1500 is a stocker it shouldn't need anything bigger anyway. You can put an extra external cooler on later if you want.

I recently replaced the oil cooler in my 73 1300 engine. It is not a dog house type. The seals were leaking and it is a good thing that I had to remove the tinware to get to the oil cooler. The tubes of the oil cooler had expanded so much that they were touching down their full length, so much so that it is unlikely that the oil cooler worked. I could not see daylight through the oil cooler between the tubes. I replaced it with a better one and at least the oil got cooled.

If your 1500 does not have a dog house oil cooler I suggest that you fit one as you will get better cooling and reduce the chance of overheating the cylinders on that side of the engine on a very hot day. If you already have a dog house oil cooler, then you have all the cooling that you need on a stock engine.