35 and 39 frames have the same frame rail dimensions, but that is about it if you are trying to build a 35 pickup that is stock. It depends on how original you want the 35 to be. The holes for mounting the front fender braces will be absent. The holes for mounting the runningboards will be in the wrong location. The 35 had the battery under the cab and the 39 frame has the master cylinder, absent on the 35, below the cab. The radiator mounts are not the same. The center crossmember is not the same. The shocks do not mount in the same way. The gas tank mounts may/may not be the same. I do not know for sure, but I suspect the cab mounting blocks might also require some additional holes to mount the cab. The rear bumper mounts would have to be added to the 39 frame if you decide to use a 35 bumper on the rear since they do not mount the same way. The holes in the front x member in front of the center crossmember are not the same. The 35 bed is a different length than the 39 bed and probably does not mount using the same holes.