1986 TUL FFW Alternator (12v) belt

Hello all.
My mrs has a 2.5 NA diesel Ninety and it's got issues with it's alternator / waterpump belt.
I've bought 2 replacement belts supposedly for it but both have arrived & are too short
the replacements are 1025 long and I wonder if theres a diferent belt for the military engines? maybe due to a larger diameter crank pulley? (is this something on ffw's to speed the alternator's when stationary??)

any ideas greatly recieved

Rich.

There should be two pulleys, the inner one being smaller. Also the alternator should adjust right in a fair way. Not ordered one for a long while, but I just get the standard civvy part number and it works fine on mine.

Larger pulls should be for the FFR generator which if fitted is on the top drivers side of the engine.