I own a 55 1/2 ton, and I don't think the frames changed much in two years. I have drilled many holes with a hand drill by first drilling a 1/8" hole and then drilling to the final size. I found that drilling the smaller hole first reduces the force required to drill the large hole and prevents the bit from moving off.
Bob


55 Cameo 396 TH 400 with overdrive
65 Caliente conv
67 BB Caliente conv
67 Mercury 1 Ton
76 GMC 3/4 ton 454ci
84 Buick Turbo Regal