Just a quick guide for anyone, like me, who is thinking about fitting OEM big bumpers and planks.
I got a lot of this from some German sites/forums and therefore this is for a LHD Van.
Front Bumper

Required Parts :
1 Bumper 255 807 111 C (1 off)
2 Bracket 255 807 115 (2 off)
3 Spring Washer N 021 241 11 (6 off)
4 Washer M8x12 N 044 147 3 (4 off)
5 Bolt M8x18 N 901 680 01 (2 off)
6 U-Plate 255 807 142 (2 off)
7 Rubber Pad 281 807 318 (2 off)
8 Bolt M8x22 N 010 241 18 (2 off)
- Holder (see photo below)- 255 804 641 (2 off) These two items may not be needed if your bumper has two vertical ribs six inches in from the ends. - to be confirmed.

Mounting:
The Bumper will be attached to the original mounting points with the M8x10 bolts & washers.
The holder (2) must be fixed (welded) to the body to that the M8x22 & washers on the end of the side brackets can fitted.
Rear Bumper

Required Parts :
2 Bumper 255 807 311 L (1 off)
3 Rubber Pad 281 807 318 (2 off) This part number changed to 701 807 318, that part number is now obsolete. It looks like it is a small rubber pad. 701 807 318 is now available from VW Classic Parts - 1,33€
4 Bolt M8x12 N 010 237 6 (6 off)
5 Spring Washer N 012 241 11 (6 off)
6 Bolt M8x22 N 010 241 18 (2 off)
7 U-Plate N 900 333 01 (8 off) A U-Plate turns out to be a Washer (M8 20mm OD)
8 Bumper Right 255 807 324 A (1 off)
8 Bumper Left 255 807 323 A (1 off)
9 Bolt M8x25 N 010 242 22 (6 off)
10 Bracket 255 807 347 (2 off)
11 Bracket 255 807 381 (2 off)
12 Bolt M8x16 N 010 293 5 (4 off)
13 U-Plate N 011 670 16 (2 off) A U-Plate turns out to be a Washer (M8 32mm OD)
14 Bracket 255 807 393 (2 off) - Available from VW Classic Parts (Ca. 6,00 Euro)
15 Spring Nut N 015 432 2 (4 off)
16 Screw 6,3x13 N 013 976 1 (4 off)
17 Bolt M8x18 N 010 239 11 (2 off)
18 U-PlateN 904 772 01 (2 off) A U-Plate turns out to be a Washer (M8 24mm OD)
Mounting:
Remove the either the bumper holders (1) or the Tow Hitch
Now fit the holders to the bumper centre section (2).
Then refit bumper holders with bumper.
The bumper side pieces and brackets are straightforward.
Planking

Required Parts:
1 LH Door Plank 255 853 953 A (1 off)
1 RH Door Plank 255 853 954 A (1 off)
2 Planking Screw. M6x25 N 010 512 1 (17 off)
3 Spring Washer N 012 006 4 (17 off)
4 U-Plate N 011 523 18 (38 off)
5 Rivet 4,8x14 N 016 201 1 (38 off)
6 Locking Plate N 900 602 01 (17 off)
7 Plate 255 853 999 (17 off)
8 Nut M6 N 011 006 24 (17 off)
9 Sliding Door Plank 255 853 964 B (1 off)
10 Forward RH Plank 255 853 974 A (1 off)
11 Forward LH Plank 255 853 983 A (1 off)
12 Rear RH Plank 255 853 984 A (1 off)
13 Holder 255 853 985 (11 off)
14 Holder Sliding Door 255 853 986 (4 off)
15 Holder Doors 255 853 993 (4 off)
Drill Ø 5mm holes as shown on the diagrams below.
Required Parts:
1 LH Door Plank 255 853 953 A (1 off)
1 RH Door Plank 255 853 954 A (1 off)
2 Planking Screw. M6x25 N 010 512 1 (17 off)
3 Spring Washer N 012 006 4 (17 off)
4 U-Plate N 011 523 18 (38 off)
5 Rivet 4,8x14 N 016 201 1 (38 off)
6 Locking Plate N 900 602 01 (17 off)
7 Plate 255 853 999 (17 off)
8 Nut M6 N 011 006 24 (17 off)
9 Sliding Door Plank 255 853 964 B (1 off)
10 Forward RH Plank 255 853 974 A (1 off)
11 Forward LH Plank 255 853 983 A (1 off)
12 Rear RH Plank 255 853 984 A (1 off)
13 Holder 255 853 985 (11 off)
14 Holder Sliding Door 255 853 986 (4 off)
15 Holder Doors 255 853 993 (4 off)
Drill Ø 5mm holes as shown on the diagrams below.
Door Bracket Holes.

a = 70 mm
b = 25 mm
c = 35 mm
d = 80 mm
e = 226 mm
RH Side Bracket Holes.

a = 30 mm
b = 15 mm
c = 53 mm
d = 365 mm
e = 60 mm
f = 33 mm
g = 65 mm
h = 180 mm
LH Side Brackets

a = 30 mm
i = 10 mm
k = 390 mm
Clean (T-cut, etc.) body work.
Apply masking tape (helps to stop the drill sliding off the mark), mark up.
Seal edges of holes with paint.
Apply a small amount of seam sealer on holder mounting face where it meets with the body work.
Planking locking screws – These rust like buggery, either buy stainless ones (Brickwerks – 23,44 ukp) or use lots of coppaslip.
I hope this is helpful.
Please send me corrections as required.
Edited to include new information.