are you sure the tubes bend up?
they could be bent to the side.
a van engine sit a little off center in the chassis to make room for the foot controls. engine mounts are slightly different from trucks also.
I used a van/mounts in my truck and engine rubbed header on pass side frame rail. truck mounts centered headers in chassis with clearance on frame rail.
truck headers can be 2x only or 4x4 only or a 2x 4x4 combo. depends on what engine/trans combos along with chassis.
4x4 headers has piped moved to clear diff/shaft up front and most times the driver side is always the same but vary on tube placement and starter clearance. some only take the low torque starter or a mini starter.
in a van the front of engine is pushed to the pass side. so if you were to stand the header up right the bend is to line the exhaust collector inline with the chassis.
laying there in the pic it does look bent upward but I am sure it is a left right bend (more or less)
they should fit from the looks but could hang down lower in the chassis of a truck and may capture the starter = remove header to swap starter.
myself I use hedman truck hedaders.
79250 in the 88 440 truck = slips right in/tucks up in frame on bottom side
I have 2 SB sets
79080 2x only = slip right in/R&R starter without removing but low torque or mini only
79171 are 2x & 4x4 chassis = slip right in/R&R starter with out removing/#7 tube allows high torque(large) starter.
**this set also fit up to 93 with a NV4500 5 speed (which the 79080 #7 tube is in the way of fitting starter with NV4500 hydro bell)
found that info when I went to a NV4500 in my 85 truck with the 2x headers.
in the past it has been my experience that the van headers will fit the truck chassis but could have clearance issues pop up on install.
same as B/RB engine B-body headers in the truck chassis. yes the fit with trimming on frame rails and hang down below frame rails on bottom also captures starter making R&R suck.
in my best guess I would say they fit but may need to watch the shift linkage/torque rod and starter R&R. looks like they will hang down below frame which may free up the room you need for linkage/starter.
***another thing is clearance room...it does have a much thinner colletor with only 2 pipes merging which is good.
