might fit..
We put a rear axle from a 71 P30 series step van(single rear wheels) into a 78 GMC pickup (3/4 ton) at the junkyard I worked at--it went right in as far as the spring pads went,--I dont think it was any wider overall,never measured it. I'm not sure it was a 14 bolt,it might have been a dana or a spicer rear end--I know it wasn't an Eaton axle...The P30 frame was very similar to a pickup,same 34 inch spread between the rails,just flat all the way back,no "humps" over the rear wheels..
But once we did that swap,we assumed the other step vans there would be the same,and we sold another one of the rear axles out of another P30 (all were 70's vintage) to another customer looking for a heavier duty rear end--it didnt fit,it was an 11,000 lb axle with dual rears,the spring pads were "narrow" like the later dually pickups!--
There was one more P30 left there with single rear wheels,we cut the rear end out of it and measured it--it was identical to the pickups rear axle he wanted to replace--but this one was a 4.56 ratio--he had 4.10's..and his was a 4x4--so it was a no go...
The one I saw yesterday at another junkyard was a later Fex-Ex truck with a 14 bolt FF with dual rears,19.5 tires with 8 lug rims-(and a cummins 4BT turbo wuth a TH400!

)-it looked WAY wider than even a G30 van 14 bolt would be--like 6 inches wider overall(a guess--I didn't bring a tape measure either!)

...Guess there are about a dozen different axles,spring pad widths,overall width,etc,--gets complicated pretty fast...
