A D70 isn't really any stronger or better than a 14FF, so get rid of the idea that a D70 is some upgrade in strength over a 14FF because it is not.
From my understanding a van-width 14FF is only a total of 3" wider (1.5" on each side) than a standard truck SRW 14FF. Now a standard SRW truck 14FF is already 3" narrower than a SRW front D60, so going to a van rear axle only makes it equal in width to a SRW front. A DRW front D60 is probably 7-8" wider than the SRW version.........so even a van rear axle will be quite a bit narrower than a DRW front.