The 8.5 was designed as a passenger-car axle. It was used in Camaro, Chevelle, and Nova (F, A, X) body styles. Wasn't even used in "full-size" cars until after they were downsized in '77. From a certain perspective, an 8.5 in a full-size truck IS "improper use".
You would be well-served by upgrading to a 9.5.
"I" would not put money into an 8.5 in a full-size truck/SUV; and that's three times as true if that axle had the evil leading/trailing shoe brakes--the 9.5 axle gets you better Duo-Servo rear brakes in addition to being bigger, stronger. I might put money into an 8.5 in my Nova, however.
Your truck...your call.