Fleetside bed installation

[64c20pickup]

Hello, I am new to this forum, I like it a lot, it is a good source of information for the restoration of my truck. I have a 1966 c20 that I am in the process of restoring I replaced the long stepside box to a new long fleetside box. there is something weird that I cannot explain to myself, when I put my new box directly on the frame, it falls lower than the Cab 3/4 "lower, yet the cab is seated on new pads only 1/2’’ in the front cab and directly to the support on back for a c20 ? Can someone explain to me what I'm doing wrong. normally what I can read on this forum is that we should not put a shim for the box, but I might not have chosen it

Thank you for help

[The Rocknrod]

3/4" that would be the width of the wood. Did you install the wood yet? Are the cross members (sills) installed without the wood to the bed?
Take a pic of two and post em up.

[64c20pickup]

the wood has been calculated already
I am really too low compared to the cab
The box is new aftermarket come from LMCTruck
Mistery

[MT65]

Originally Posted by 64c20pickup

the wood has been calculated already
I am really too low compared to the cab
The box is new aftermarket come from LMCTruck
Mistery

Easy fix, unless your a die hard traditional restoration guru, shim it up….nobody will know till you tell them…..

[forestb]

I now that when I had my cab and frame off of my frame the new pads under the cab and core support had to be trimmed in order for everything to sit at the same height. I have a step side and the bed sits a little higher than the cab than I would like. They sell rubber pads for between the bed and the frame.