I know someone did on a Savanna van, but I forget who off hand. . . . So yes it can be done, another option MIGHT be to dill new holes farther back on the frame. It will all depend on how the bumper brackets are mounted on the van.
My van :
1991 Dodge B-250 (Junk Yard Dawg)
5.2 tbi V8, auto trans, and junk yard parts....
Founder & President of Sooner or Later United Truckers and PROUD TO BE A S.L.U.T. ! !