That thing brings back memories of the two C3500 CCLB work trucks I had in the Marines. Nice.
The front actuator in my '92 Blazer K1500 gave out AFTER I moved to SoCal. Went wheeling one day, used 4x4 a bit, went back into 2wd, then tried to put it in 4x4 to climb a hill to leave and nothing. Put a Posi-Lok in after that and all was well.
My friends' dad's trick for the fender flares was a heat gun. Heat the flares up enough to make them a bit more flexible and install them. By the time they cool you should be able to pop them right in...
...but I would say you're on the correct track to even see if it fits the holes first.