They are right a spring drop on an I-beam front end does cause excessive tire wear. But, a merc front end swap is not your only other option. About 3 or 4 suspension manufacturer make drop deams for this era of truck. DCM suspension is one I know of for sure. There are a couple more out there. I wouldn't recomend using the "Dream Beam" drop beams if you are going to use it to haul anything. They don't hold up as well, from what I have heard. Dropped I-Beams are made, I just can't remember a name. Try
www.justIbeams.com I think that shoudl get you something. Just airbags.com will get you to the site and let you search from there if above doesn't.
Scotty