Timing belt and 2-piece crankshaft hub ('89 325i)

[John Smith <john@xxxxxxxxxxxxxxxx>]

Can someone please enlighten me about the business of replacing
the timing belt on my '89 325i.

I have a Bentley manual which
tells of a "two-piece crankshaft hub" on some models. I'm not
clear how/if it's possible to tell which I have *before* starting
to do the job.

This seems a pretty important thing to find out as
it the hub mounting bolt is done up to 410Nm/302 lb/ft!!!
If I have one of these I guess I need more than my 1/2 inch
socket set to undo it. 

Looking at the engine I can see the three pullies (which seem to
be one piece) that the v belts for alternator and power steering run in.
Behind that (towards the block) there's a large toothed wheel -
for the engine timing sensor. This seems to me to be a separate
piece from the pullies. I that that what "two-piece" means? 
I can't see anything further behind that (where the timing belt
actually is).

Mention is made od a holding tool BMW 112 150 - can this be made up 
easily or is vital to get from a dealer?

I wouldn't mind tackling this job - it's just *that* bolt
that's the (possible) problem.

TIA for any pointers on this.

- -John

------------------------------