Late XJ with earlier 4.0

Has anybody successfully done a swap such as this? I can't seem to find a concrete yes or no.

2001 XJ 4.0, bad engine, have my eyes set on a '96-'99 4.0, the XJ is already set up to use the 0630 cylinder head, so the head is not the issue. My concern lies within the timing set. I'm worried the earlier single roller timing chain will allow too much variance/deflection in valve train timing due to the inherently less taut nature of the single roller chain versus the later style chain. The late/distributorless PCMs seem significantly more sensitive to changes in cam timing than the earlier systems ever were. I do not want to swap in an earlier engine and chase driveability issues.

Cliff notes: Has anybody 100% successfully swapped in a complete pre-2000 4.0 in a '00-'01 XJ and had it run exactly as it should?

You should be fine. If you are concerned about the timing set put a new one on it. I've ran the single roller, double roller, and silent link chain on my 2000 and the PCM never bitched about it. I've also used the snubbed block and have gone without it.