very good info-thanks
HOWEVER... when i told Mar-K what i was measuring, they couldnt find anything that matched.

someone else has mentioned that even if only x cross sills, there are still bolts with only washers behind inbetween sills in a front/rear pattern.

not sure what you mean by skids since angles also have riased skid rib too.

im pretty sure its a 56 i KNOW it was/is a stepside. know its a longbed, know it came off 3/4ton, and i KNOW that some of the angle strip holes held fender braces-i took them off.

bed started life in the high80's length inside and it is now 71.25 inside.
http://yepthisismylife.blogspot.com/