Re: XH longreach 99' questions...
Go the xr6 head and cam! I’m not sure whether it changed later on but when they started xr6s the valve springs were just the stiffest 10% of normal valve springs (they vary a bit). Valve springs have absolutely nothing to do with compression ratio by the way. There might be a slight difference in the combustion chamber which might raise the compression ratio a bit but there is very little difference between xr6 and normal anyway – it might make a couple of hp more but won’t need pulp. I haven’t heard of any differences with the throttle body.
What sort of XH is it? 1 tonne versions have a 3.45 diff anyway I think.