Rear Suspension , new shock question

[06SuperDutyF250]

I bought my truck its an 06 F250 XLT. It has in the front What looks like a red spacer between the coil, i know its a leveling kit, but dont know by how much, the truck sits real high, and I like it, it also has in the front 5100 shocks bilstiens. The Rear appears to be 4" blocks with stock shocks. the truck has a gvwr of 10,000lbs on the side door. But i want to know if these blocks are stock or the 350 ones. I want to put 5100 in the rear but dont know which ones i should get, any help and input would be appreciated, i dont wanna throw money and it be the wrong shocks. the truck sits almost completely level.

[PGreenSVT]

Stock rear blocks. 5100's for stock F350 will do the job for you.

[06SuperDutyF250]

so my blocks are 350 your saying?, which bilstien 5100 rear part number is it? thanks