by Mark Nixon » Mon Jun 25, 2012 6:33 am
They are the same crossmember if the frame heights are equal and it's the same era ('88-'93).
There ARE 2 different crossmembers in '88-'93, the "tall" frame one has an extra riser riveted to it, making it look like a double crossmember.
With gassers and diesels the only things that MIGHT are the pieces between the trans and the crossmembers on 4x4s. The "mounting isolator system" if you will.
It's the height of the rails that matters, which makes a tall and short frame crossmember different.
I realize you want to do the 1991-1/2 D-250 (short) frame to 4x4, so if the donor is a tall frame truck, you'll have the right crossmember, just buzz the rivets off and remove the riser.
Mark.