Dana and Spicer are two names for the same company. The Dana type 45 is a real oddball- - - -very limited production and repair parts are unobtanium. It's possible to use a Type 44 ring & pinion gear if the rest of the parts are good, but things like axle shafts, side gears, etc. are different (heavier) than the type 44 which has been used in dozens of applications- - - -GMC, Ford, Dodge, International, Jeep, etc. cars and trucks.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!