The engine in question is an Alpina engine used in the E46 3 series B3S and the E85 Z4 Roadster S.
The roadster S's only came in Manual format and the RHD UK spec B3S's were all switchtronic auto.
The Engine as mentioned is based on an Iron block M52 aka the S52 used on US spec E36 M3's and shares nothing with the M54.
They are 3346cc and everything is custom on the bottom end, crank rods and pistons. The give 305bhp and 267lbft.
The most common problem they suffer from is head gasket issues and a head gasket (which is unique and Alpina only) is £300!
All the parts used to fit an M52 to an E360 can be used ie the E34 sump, E36 mounts etc but as mentioned the electronic side of this will be expensive/tricky to sort as they are E46 based and the DME (engine ECU) will be looking other control units on the PT CAN like the EGS (auto gearbox), DSC (traction/ABS) and there will also be EWS dramas.
Using an E36 M52 Siemens DME and throttle body with cable will loose you power, the Alpina "fly by wire" throttle body is massive!
Using the original DME, loom and throttle body is a must and if there are people out there who can sort the PT CAN issues on S54 DME's then sorting the Alpina one shouldn't be a problem i would have thought. They are all Siemens DME's after all.
The engine is the ultimate incarnation of the M5x family and would be epic in an E30!
Here some pics and a little info on my old B3S.
http://www.e30zone.net/modules.php?name ... hlight=b3s