amost a pro-street............& rim size question......

[QKENUF4U]

won a set of 31x18.5x15 tires off ebay, had the guy use DHL to ship them since they where pretty much half the price of UPS. anyways, i had the DHL guy throw them over my wall on tuesday, come home and theres only ONE TIRE . i sold a guy on here my GMC tailgate and we shipped it out yesterday using DHL. i was here when he showed up to pick the tailgate up. walked in my garage to get the tailgate and he seen the other tire, ask me, you missing a tire ???? i was like hell ya !! he said "its sitting on the dock illl drop it off tomorrow (today), well today has come and gone and no tire. im gonna call tomorrow and raise hell, let them know it sitting here in phoenix on the dock and i want it TODAY !!! so anyways, after i get the tires and figure out my backspacing (i already ask and got an answer but i want to make sure its gonna work 100% for my tire/rim setup) im gonna order my rims.
my question is.......... will a 5" rim work on the front ok on a BB truck that isnt used for anything but cruising around a bit and hauling a motorcycle every so often ?? i want the fatty/skinny look so i want to use the 5" rim with like a 185 front tire, will that support the weight ok ?
ill have pics of the old back tires disappearing in a couple weeks once the new rims arrive.
thanks
lance