My TJ Auto has an oil leak that I am having trouble finding. It is behind the engine (towards firewall). I suspected rear rocker cover gasket, which I replaced 2 years ago. Some oil gets onto the rear exhaust heat shield (resulting in burnt oil smell). Oil has also fallen onto the auto selector cable and it has swelled. I can't see or feel leakage from the rocker cover and have tightened the bolts, without stemming the leak. Replaced distributor o-ring 6 months ago and today felt under distributor and no signs of leak there.

Is there anywhere leakage could occur on back end of motor other than rocker cover (leak is way too high to be sump and I checked sump, which is fine)??

Have you got underneath the car? If the engine is a dirty and its masking the leak, youll need to degrease it and then recheck. Id still bet on the rocker cover gasket! I used to own a couple of Cressidas and blown head gasket were so common, it was fitting to use an acronym (BHG). Its about time us 6G74 owners started saying RCG!

+1 on it being the rear rocker cover gasket.
They can leak if hardened with age or the bolts aren't torqued up accurately. Too tight is worse than too loose. Warps the cover.

The oil leaks down onto the exhaust expansion joint and takes a long time to burn off after fixing the leak. A good squirt of engine degreaser on the joint - engine cold - helps.

In February I had some extractors fitted and the rear spark plugs changed on the same day. Immediately after I smelt what I later realised was leaking oil dripping onto the hot rear exhaust manifold heat shield like the OP. I also noticed that the oil must have been topped up because it was reading significantly above the 'high' mark on the dipstick which it did not before. Without knowing for sure I guessed that the extra oil was causing more pressure (or maybe just sloshing higher) and forcing its way out. I have never had an oil leak before and almost never had to top it up. (My TL has not quite done 120 000 km.) My guess for the source of the leak was also the rear rocker cover gasket, with a second guess being that one of the new spark plugs was not in tight (is that likely?). Over a few hundred km the leaking slowed and is minimal now.