Update from JG Design & Fabrication on the Monster build.
"After laying our spring fixed position, cycling the suspension, and determining our shackle mounts while giving us 45* degree shackle mount. We used a hole saw to drill the frame at 1.5" hole, then cleaned the holes up to make sure they were straight and level side to side. To verify our side to side trueness we run our bushing sleeves in the frame with a 1.25 OD tube through the frame / sleeves. Once leveled and squared, we tacked each side inside and out, then welded it out. We then ground our welds out, installed bushings after greasing with wheel bearing grease. Then a simple shackle install and there we have it."