2002 V40 1.8 SE LPG Gearbox

[SteveV40]

I know this might appear strange for an LPG Forum post, but please bear with me.
The 5 speed manual gearbox on my 220k 2002 V40 1.8 SE LPG failed at the easter weekend, making some pretty horrible rattling, grinding noises. All gears are affected, and it needs a replacement box. I have been trying to find a second hand replacement, but have had a tough time identifying the part.
I think that the part number is 30613755 (although oddly there is also a 30613577 Manual Gearbox, which is an uncomfortably similar part number!)
I have been unable to confirm the part number label or stamp on my gearbox, which is still in the car and consequently not easy to look at easily.
I can find plenty of 577's on the internet, but these dont look like my box, and I cant find any 755's in the UK at all.
A local specialist Volvo breaker has told me that the part number is irrelevant (which I dont understand) and that the box he has will fit.
Does anyone know if the 577 will fit? From what I can figure out, the clutch fork (excuse the terminology if it is wrong) would be about 90 degrees further anticlockwise (if facing the engine). Now, initially, I thought that this would be unworkable, but I guess if the hydraulic pipe was extended to meet the now position, it might not matter after all. I dont want to be guessing at this, so would very much appreciate any help, as I suspect that the 755 gearbox may be specific to the LPG model although, having said all that, the general confiuration on my LPG car is similar to the V40 1997 2.0 CD that my missus drives!
Does anyone know the answer to this, or where I can get a second hand 755? Many thanks.