GPz750 Steering stem length

Hi All.
I recently bought a 1985 GPz750 Unitrak bottom yoke to use the stem for my ZX9 fork conversion, I was hoping to get everything sourced & trial built before I pull the front end of my GPz.
But just holding it up to my headstock the new stem looks approx 15mm longer than the one in my bike, the bottom yoke & the machining to the top threads & bearing surfaces looks identical just a longer stem.
Before I buy another I wonder if there was design change through the range or was it just that the one I bought was misidentified (different variant), I will ask potential sellers to measure the stem before I buy.

Are you planning on pressing out your old stem and putting it in the ZX9 triple? If so, cut it to the correct length and have a bushing made.

I was not planning to use mine so bought what I thought was the same part as the one in my 85 GPz750. sadly the 'new' stem doesn't have enough lower bearing surface & don't really fancy the thin wall of the required sleeve so probably going to need another stem.
Looks like there was a change of stem mid production
1984 & 85 = 44037-1111
1986 = 44037-1161
Just need to sort out which is which (long/short)