chiming in a lil late but here goes. i have the black diamond which you speak of. but it in the mid-late nineties. anyway, it has been moved with me to three different states(Texas, n.m and florida). still only using bolts to hold the firebox on. no rope or any chemical bonding. leak is minimal at best. like what was proposed earlier, take the time to properly tighten the bolts with a good lock nut and i feel that you will be fine.
matter of fact, the only mods i have done to mine was to make a charcoal basket for it. while you are refurbing, don't forget to make a plate to protect the bottom of the fire box from the heat of the fire. it came with a preformed steel plate that rested on the bottom of the inside of the firebox and works wonders.
i did move the thermometer also. and i changed the grates out to one long sheet of expanded metal cut to fit snugly in the smoking chamber. i guess after all this i ought to take a pic or two. haha