Thread revival on this,
I've chatted to Thom, and might make a separate conversion thread section as it's been a big read to get the basic needs for just a later engine swap 
I'll update this with more once it's fitted within the next few weeks.,  EA to EL engines are getting rarer in the wreckers, and this AU engine was chosen due to listed low kms (176,000) and AU head gasket is better than a risk on anything older possibly cooked due to head gasket issues.    a mate of mine is about to (hopefully) put an AU series 2 engine in an XG current parts gathering and testing has got the engine mounted with the following. (BA alt mounts same as AU2/3 and he had it on a barra engine he was considering using) AU2 engine
XG dissy
XH air con bracket
XH air con compressor(need custom hoses to work on XG?)
XH belt tensioner
BA alt(because he had it)
AU spec water pump and power steering will have XG exhaust manifold and XG intake
XG thermostat housing/temp sender Tuff mounts Sway bar for AU/BA     some notes @SPArKy_Dave might be able to confirm? will this patch loom allow a BA alternator to be used in an XG with AU 2 engine, or an AU 2/3 car?https://www.efisolutions.com.au/3-pin-alternator-patch-harness?gad_source=1&gclid=EAIaIQobChMIhJL2pKHnigMVVw6DAx0rLzuREAQYASABEgLvzfD_BwE    
Belt is yet to be confirmed, but it might need to be a custom length, however after looking up the sizes. estimated after measuring  this seems a close size 6PK2480   6PK2690 EL V8 shown in pics below way too big.  6pk2380 AU Belt appears way too short when tested 6PK2400 XH belt also too short when tested 6PK2510 AU VCT (likely to be tested soon, will update this shortly)    some photos that might help when i redo the conversion thread.  Thom's engine back from page 1
  XH air con bracket from today's conversion   the set up that would work if you were running a BBM (broad band manifold from EF to AU ) 
  log manifold doesn't clear the air con pump
  this is the XH air con bracket and pump and tensioner with the log manifold from XG 
  basically the above with front view (V8 belt fitted just to check the belt path doesn't cross the intake on throttle body)  

Hey thanks for your help everyone, turns out that for some reason he decided to sell the car which he paid $3500 for $100 to a guy who is making it a paddock basher even though he was previously offered over a grand for it. He decided to tell me this afternoon even though he did it a week ago. So theres some time Ill never get back chasing parts. On the flip side this thread has given me some useful info about btr boxes.

Just to clarify a bit , up to AU internal wiring is grounded inside the transmission .   From BA on , the internal harness is different and the grounds to all solenoids go back to the ECU , so they are a no go.   There is also a variation in AU I came across . Although the internal harness looked the same the plastic plug into the case was a different size/diameter than the earlier models . Not really an issue . I only came across it as a mate built one , wanted to use the late case , then found his earlier case from a V8 EB or ED or whatever it was different where the harness fitted . Luckily I had an AU harness worked 

I'd imagine many earlier BTR's would be fairly worn out by now, either clutches, or even just the second/fourth band?   Not to mention potential gummed up solenoids, or valvebody?

interesting, 
A mate of mine's Dad's AU ute has an EL trans, and he's about to fit an AU trans in an XG (using XH transmission loom) 
wonder what's actually different. i'll reply here if he finds any issues with this combo. (assume the AU with EL trans used all the AU stuff though) 

Speedo sensor, gearshift indicator (sometimes referred to as neutral safety switch) and wiring loom, only external, internal wiring doesn't need to be changed

what electronics do you mean for this Thom?

   

All au trans will be a straight bolt in, just make sure you use the electronics from the car as one of the years has a different gear position indicator and I can't remember which one

Ok so b series transmissions are a no go? Ill see if I can get one from an au, any difference between year models?

Ea to au btr's are mostly interchangeable, in 6 cylinder cars with another 6 cylinder btr (some v8's had sports shift like ed sprint, el gt, au ts50 etc) to use an earlier btr in an au it is recommended to fit the au bellhousing to the e series transmission (straight swap make sure you get the converter re seated correctly), the e series bellhousing wilbolt to the au engine but it won't bolt to the sump, you'll need to use the au speed sensor, neutral safety switch and wiring, ba an later btr's can't be used in a ea-au (except maybe column shift ute transmissions but im not certain on that one) as they don't physically have shift positions for 1st to 3rd and are setup to run with the "sports shift" shifter, also unless it is a ute transmission it won't have a mount for the speed sensor (without it the transmission won't shift) as ba to fgx (except ba utes) all came standard with abs and use the abs sensors to tell the ecu how fast the car is going for controlling shift points