I used a Reese Towpower 51016, no cutouts needed. Although I did do a small reduction in the depth of the hitch side panel to increase clearance. I also moved the hitch crossbar slightly forward so the 1/2" pin holes lined up with the pintle base holes so I could tie together with a 9/16" grade 8 u-bolt and two thick SAE grade 8 washers (drilled the pintle base/bumper holes out to 5/8"). Also swapped all hardware to 1/2" grade 8 fine thread with conelock nuts. I did need two sets of the square 1/4" plate washers and used the second set of thick grade 8 dished washers as well (two per bolt) to clear the military bumper reinforcement mounting bolts.
So now, as the unmodified CUCV hitch/bumper and the Reese hitch are solidly tied together (1/2" thick spacer between hitch tube and bumper made from 4 unused 1"x2"x1/4" hitch washers), I can do 15,0000 max pintle tow, 800# max tongue/pintle wt, 8000# max 2" ball tow and 1300#/ 13,100# with a weight distributing hitch.
The U-bolt was custom made by Kevin from autospringcorp.com in Boise Idaho for $13.85 shipped on a 2 day turnaround. 208-362-0431 (4.25" deep. 2.75" inside width - the one shown was a 5" bolt I cut down to 4.25")