So, looking for a new valve cover. Not the plastic, but the aluminum cover. Tasca only lists it with the entire head, and I'm guessing other wholesale websites are the same. Is it not possible to buy ONLY the cover, and not the whole head?
There are no bearings in the head. I'm not real sure why people say that should be matched? It's all about oil ports and the cam seals. The cam spins around in the slot of the cam cover and the oil that is pumped up there keeps the cam from binding. The cam seals stops the oil from coming out. Just get a matching cover from a junk yard. Wait... why would you want a new one anyway?
What he meant was that the cam journals are line bored at the factory with the cover in place, meaning that there is a chance of a small discrepancy between covers. While it likely won't be an issue, there is a small chance that the journals don't match and the cams could bind up.
NA cams into a T5 is fine because the cam cover isn't being replaced with the cam. It's still matched to the head. Swapping cam covers is one of those things you're not "supposed" to do, but I'm sure there have been ones that have been successful in completing the job.