The diagram below is what I used for the mud flaps installation. Number 140 is the Metal Fender Rail and number 70 is the clips for the front. I did not follow the direction for the bolts for the rear ones. I have the nuts on the aft side and the bolt on the forward side of the frame rails (number 135) to have more clearance with the fuel tank. Since I had already removed the factory running boards, for the front mud flaps, I use the non-running board version. Vlad from fourbyfourclub.com showed front mud flaps that are compatible with the running boards on his website.

Edit: just looked on fourbyfourclub.com website and the front mud flaps that are compatible with running boards are not listed. You may want to give him a call anyway.

I purchased these previously-owned front mudflaps and ordered the clips (U-shaped clamps) from Eurotruck Importers. Note the mud flap PN's are for the non-running board version; hardware for the front are also listed.

Left Mud Apron, Front, PN A4638890105
Right Mud Apron, Front, PN A4638890205
Clip, Mud Apron, Front, PN A4638800093 (Same for Left and Right)
Hardware per side: All hardware are 18-8 CRES
M6-1.0x20 Hex Head Bolt
M6-1.0 Nylok Nut
M6 Fender Washer (2x)

Got the rear mud flaps from Eurotruck Importers and installation is very simple. Vlad also has the rear mud flaps if you prefer ordering from one source. I picked up all the hardware from a local hardware store.

Left Mud Apron, Rear, PN A4608891105
Right Mud Apron, Rear, PN A4608891005
Rail, Fender, Metal, PN A4608820027 (same for Left and Right)
Hardware per side: All hardware are 18-8 CRES
M6-1.0x20 Hex Head Bolt (3x)
M6-1.0 Nylok Nut (3x)
M6 Flat Washer (6x)

Note:  The long M6 bolt (circled) is reused, holding the inner fender to the frame rail.

@ fsedak: The front mud flaps shown in the photos are not compatible with the factory stainless steel running board like those shown below. The molded-in triangular extensions interfere with the running board front rubber caps.

On Vlad's website, these were the mud flaps designed to work with the running boards.

http://fourbyfourclub.com/W463Accessories/W463MudFlapsClassicFront.htm

Thanks!

I'm currently still at stock height. The springs on my G500 are two-striped yellow-orange front and rear (AFAIK, these springs are original from MB). Here are the measurements with my BF Goodrich All Terrain in LT265/70R16 at 32 psi (OE size and pressure). Fuel tank is between 1/2 and 3/4 full.

A = distance from the ground to the bottom edge of wheel arch

B = distance from center of wheel to the bottom edge of wheel arch

C = distance between top of tire and bottom edge of wheel arch

Right Rear:

A = 35.25"

B = 21"

C = 5.5"

Left Rear:

A = 35"

B = 20.75"

C = 5.5"

Right Front:

A = 34.19"

B = 20.19"

C = 4.5"

Left Front:

A = 34.19"

B = 20.19"

C = 4.5"

Hope the info is of some use to you.