Can you alter the travel internally or do they use different internals and stantions for the 150mm's?
Bump!
They can go down in travel from factory setting; but not up, I believe. Exceptions being the F29 and 831 models.
......some OEM forks are speccced with a reducer by the manufacturer to balance a full sussers front and rear suspension. This was certainly the case with the 2007 Stumpjumper 120, the Fox fork matched the rear of the bike in travel but was infact a 140mm Float with a 20mm reducer fitted - it was removed by many people come the first service.
We are talking 32's and not 36's right? 150mm 32 Floats are a more recent fork but if your Floats came on your bike (or were an OEM fork you picked up somewhere else) and your bike is a full susser and they are quite a new model year fork then they may be reduced 150mm forks but I wouldn't hold your breath.
If not then I think longer internals and stanchions will be required so for 10mm it's probably not worth it.
Get 150 and shorten. Gives you flexibity to go down to to 100 if you want.