I had a 98 Chevy Express 2500 I used for servicework... Loaded to the gills with full rolls of #6 and smaller, MC cable, conduit, boxes, tools, etc... I had 1 ton springs added and a set of Monroe's re-flex shocks and it handled the weight a lot better. I had some pretty stout "E" rated Kelly Safari's on there too.

I managed to pull a trailer with a Bobcat and all the trimmings from Glendale to San Diego and back... The tail end sagged theatrically, but it never felt loose. Passing took a weeks notice at anytime though. whistle