47-55.1 Body mount options 51 AD

[R&B51]

I’m not the best on site searches, maybe already covered in past.
Making custom frame. Rolling chassis swap under truck. I’m close to designing tube rails to have done locally.
Planning to mount cab and bed directly to custom frame tabs. Any advice on what kind of body mount use? Cab mounts will be brackets off tube. Need ability to shim, tweak final fit.
Seems what I read says stay away from rubber and old style OE pads due to age, compression and settling body out of true.
Problems with direct mount rear cab since no heavy hauling?
Silicone, polyurethane, any experience with particular maker or kit?