So just double checking there's no rule about the forward point of the draw bar being above the frame rails provided it's centreline the rear diff? When I built mine it was with both NTPA/PPL and the NHRDA copy of the rules and didn't see it if that's the case.
I don't see anywhere that it's illegal in NTPA or PPL. In 2.6 if you have to cut the bed theres a bit of a grey area from what I see:
"The body must be the OEM truck body, including the full
bed floor."
Otherwise it just says it must be frame mounted:
"Hook point must be no closer than 44” of centerline of
rear axle, hitch height maximum of 26”, with a minimum
of a 3.75” X 3.0” opening. Hitch point must be easily
accessed. No “trick” type hitches permitted. Hitch must be
stationary in all directions. Hitch must be frame mounted. Hitch must be mounted centerline of rear axle or behind.
Hitch must not exceed a maximum of 25 degree angle from
pivot point to hook point. No hitch supports or adjusters, if fastened to the rear axle housing shall be above the
center line of the rear axle. Pivot pin of drawbar can be no farther forward than centerline of the rear axle."