Here's one shop in San Diego that definitly does Isuzus anything. This is Stinky Fab, Dallas is the owner and chief builder.
I know him personally. He's still running one of my engines. Tell him I sent you. He's one of our regulars guys at Moab every year. Heck, he's been there more times than I have.
He was in my Rodeo when I broke my FF rear Dana 44 and had to drive it home to Texas on the front axles.

Dallas can help you get your custom built stuff started anyway.

Then there's Matt at Independant 4X He can help you find those hard to find parts for Isuzus. Matt is another Moab buddy who definitly knows how to Hot Rod an Isuzu. Not many aftermarket Isuzu parts suppliers our there.

Heck even my shop "Ridiculous Equipment is still a private build shop.

Look through their Web Sites and study the Rigs in the Readers Rides. If you want to build your Rodeo, then this is where to find out how.

Best of luck there Ty.

Curtis