Cut the rind from the watermelon (you should have 4 1/2 lbs of rind); trim off any pink flesh and the green and pale green outer skin and discard.
Cut the remaining rind into 1-inch pieces; you'll have about 9 cups of rind to pickle.
Place the rind in a large nonreactive bowl; in another large bowl, combine 6 cups of water with the pickling salt.
Pour the salt mixture over the watermelon rind, adding more water if needed to cover; let stand, covered and at room temperature, overnight.
Next day pour rinds into a colander in the sink and rinse well with cold water, letting drain well.
Place rinds in a large pot and cover with cold water; bring to a boil, cover, reduce heat and let simmer until rinds are tender, about 20 to 25 minutes, the drain again.
Meanwhile, make a syrup in another large nonreactive pot, by combining sugar, vinegar, 11/2 cups water, cinnamon, and cloves; bring to a boil, stirring to dissolve sugar, then reduce heat and let simmer, uncovered, for 10 minutes.
Strain syrup, discarding solids; add rinds to syrup, bring to a boil, reduce heat and simmer until rinds are translucent, 25 to 30 minutes.
Pack into hot, sterilized jars, leaving 1/2-inch head space, wipe rims clean, tighten lids.
Process in a boiling water canner for 10 minutes (begin timing once mixture returns to a boil); remove from canner and cool on wire racks.