What is the normal life span of the timing chain & tensioner and the oil pump? Engine is out to make clearance for other work, but was running fine before. As soon as I get the engine all cleaned up and the years of oil/dirt off I will pull a rod bearing cap and see what the bearings look like, and may use that as a guide to the oil pump. Does the R53 tend to wear the rod bearings evenly or is there one I should focus on? The job is quickly getting out of hand with the “may as well while i’m In there” routine so starting to focus more on the likely issues.
2002 MCS 142k mi. Original owner, all stock (so far).

 

Timing chain failures aren't very common on these engines. So, if I were in your shoes I would probably inspect the chain for "stretch" and if it looks good leave it alone. I would proactively replace the chain guides/tensioner since they're plastic and get brittle with age.
Definitely replace every seal and gasket while it's apart (I think this goes without saying) because Murphy's law says that if they aren't leaking now they will as soon as you put the engine back in.
A new oil pump can't hurt, and you'll already have the TC cover removed which makes swapping the pump out very easy. Don't forget to prime the new pump.
Rod bearings should all wear evenly but you should check all 4 since "you're in there".
Main bearings area bit more work to check but if the rod bearings are within spec I would assume the main bearings are good too.

A few other things:
-Replace the oil pressure sensor. Failures are common where oil can leak into the wire harness and cause all sorts of problems
-Replace every single coolant hose and plastic fitting (even the metal pipe along the subframe if it's showing any signs of rust). This job is infinitely more easy with the engine removed.
-Inspect the cam lobes. It's not common but they sometimes wear prematurely
-Perform a leak down test prior to installing the engine. Burnt exhaust valves are another known (but not common) failure point on these engines
-Harmonic balancer and belt tensioner failures are also common. Use your judgement here knowing they're much easier to replace with the engine removed (more so the tensioner)
-Make sure your motor mounts are good, particularly the upper passenger side one.

That's all I can think of for now.

 

tensioners fail often, guides wear out too in fact a guide failure is the only real bad failure i've personally had in all these years of owning R53s

 

This one's a big day ruiner when it fails. Limp home mode, stinky burning rubber smell, no air of course, very distressing. Recommend bite the $400 bullet and swap in an ATI before it happens. You can 'size up' to a 2% or just keep the stock diameter.

Mod MINI has a vid on it on YooBoob.

Also, coolant expansion tank - if it turns brown, don't leave town; it's soon to go splodey all over the place. Consider upgrading to metal.

 

Or go crazy and get the 4% shell from RMW

 

This is one of the upper rod bearings out of my engine that had 165k miles on it. This was the worst of all the rod bearings, though I cannot remember from which cylinder it is, although I want to say cylinder 4.



Note the copper hue coming through. Overall, I was pleased with this wear. I have owned the car since new (May 2003) and have done all the oil changes myself using various synthetic oils (Castrol, Mobil 1 and most recently LiquiMoly) at around 10,000 intervals. Some of the early oil changes I actually did run to nearly 15k miles. My car is daily driven and sees regular trips to redline. I still haven't looked at the main bearings yet - the block is on the floor in my shop - but I do not expect there will be any surprises when I get around to it. I have an engine with about 76k miles in my car right now since I overheated my original engine when one of the plastic coolant tees broke off one evening on the way home from work. I have a whole thread on that escapade.

A couple or three of my cam lobes had pitting (cylinder 1 exhaust was worst, cylinder 1 intake and cylinder 2 exhaust less bad) that I attribute to material failure rather than a lubrication issue. Below is cylinder 1 exhaust cam lobe.




Perhaps with that information, you can extrapolate how your bearings may look, but I would be curious to know (and see) how yours look.