Actually, as long as you weld the blocks to the axle, it is perfectly acceptable to put a block between the springs and the axles. Make sure that you use a new index bolt in the sping back that goes through the springs and the block in order that you properly locate the axle (the axle has a smal depression in the spring plate for the bolt head to fit into...). Blocks are used not only by folks who installed the older military Hercules DT3.7 repower kits, but also by folks using Detroit or Cummins power... Military installed blocks on the left side as part of the kit to install the spare tire on the side carrier (the "door mounted spare").
Want me to send him some photos of my axles...?