Don't worry about that, the covers are all the same. Many people have installed oil coolers directly to the 03/04 cover with no modification required.

 

If this doesn't work, I put an aftermarket cooler on my 2003 with a sandwich adapter at the filter.

Been very happy with it, and the price/install was easy. I do everything I can to help the disco out here in the desert, 120F+ is hard on things with motors..

https://www.amazon.com/Rev9Power-Rev...S2F6P7AQM754Z9

 

Thanks for the info that a 04 front cover will work when adding an oil cooler. The problem is that oil cooler lines are not available anymore and used ones are hard to get and might need replacing the hose. So I am going to make my own lines. Will M20x1.5 to AN adapters like these -> https://www.summitracing.com/parts/vpe-16628 work instead of the tube/nut on the front plate?

How to get these sealed? Here are my options:

1) 12mm crush washer in place of the O-ring.
2) 20mm crush washer on top of the cover
3) just teflon tape
4) combinations of the above

For the cooler I found 14mm compression fittings. To make them AN I found adapters in my local hardware store. The rest should be straight forward - metal braided hoses with AN ends.

 

Finally I installed my oil cooler (stock connected at the front cover ports), but there is no flow. The cooler fittings are cold and I see no difference on oil temperature. Looks like the 04 front cover is really different and does not work with oil coolers.