What are they?

One is for a GS-R and the other is for an LS/RS/GS.

Okay that was a tough one then. My question should be more detailed I guess.

Would a GSR header fit on an LS head and vice versa? What about an LSVTEC conversion? Would the GSR header fit and bolt right up to the exhaust?

No the GS-R header won't bolt-up to the LS, it's a different bolt pattern. For the LS/VTEC, you'd use a header for the head you have. I'm not sure about bolting up to the exhaust.

So now that I have a VTEC head the GSR header should be able to bolt up?

All the B series motors have the same bolt pattern on the exhaust side of the head. But the difference between the GSR and LS header is that the GSR header will not have a O2 bung in the B pipe part of the header, also it will be sightly shorter.

Well I'll be damned, glad someone corrected that.