67 72 cutting down stepside

[gmc684x4]

I am looking at shortening a long box stepside

I read on atleast 1 thread the numbers on the stepside are
15 inchs on front and 5 on the rear to remove


On a fleet side the numbers are well stated 12 and 8 inchs to remove

Cutting the frame is well documented with efabman and stacy on gears tv

Looking at doing what planned 29 years ago when got my68 before i made her a 4x4
2/4 drop 5.3 ls either 4l80e or 6 speed i has in my camaro