Any body no if a 1998 rear subframe is the same as a 2005 rear subframe.
The part number for the sub-frame is: 91407500. fiat multipla.

Where did you find that number?
Only reference I can find (so far) is this one . . .
91407501

Again, as with the Towbar question in another thread, I'd be surprised if they altered anything major between the Original and f/lift models.

I did notice the front Sub-frame 'bushes' on my current (02 110 JTD ELX) are shorter than the ones on my old one (02 115 JTD ELX), and as Fiat only supply complete Sub-frame assemblies (with mountings fitted), maybe the difference in part-numbers (and/or between early/late models) is something minor like that.

Try ringing your local Fiat dealer's spares dept, they'll have the info.

Edit; EPR listings

off ebay strongarmsidley is selling the frame its two years old and off a 1998
He did put 1998 to 2010 but now changed it to 1998 to 2002 compatible.
I was going to have a bid on it but think ill leave it just in case its wrong fit.
many thanks
Mel