Alternator swap

I have a 2000 GMC sierra 4.3, I swapped the noisy oem alternator (105A??) with a new take off 150A alternator (2006). same manufacturer, same plug, bolts right up. The new one bench tests ok but will not show a charge on the vehicle. Any Ideas?

broken wire/fuses all ok. or the new alt may fit but not be mated to the truck wire.

I had issues with case ground on my alternator. It was a brand new alternator and I was getting headlights dimming and an occasional battery light.
I checked everything and gave up, pulled the alternator off and roughed up all the engine mounts with sandpaper and the problem went away. Hindsight, the engine mounts for the alternator were aluminum and pretty corroded.
Good luck