93 Chevy 3500 transfer case

My friend has a "93 Chevy 3500 4WD with a 6.5 turbodiesel, automatic
overdrive.
The transfer case let go inside and tore things up pretty badly, but
he was told there's a problem with getting another one since that
particular unit is for " '93 only."
That seems rather hard to believe that a transfer case is only used
one year (with all the hundreds of thousands of similar Chevy trucks on
the road).
Anyone know if this is accurate or if his techincian is misinformed or
"something" ;-)