Measure the internal height of your van this can be with in 100mm of the roof or up to the height you can comfortably fix and scribe the units to the side.
L1 H1 Transit Custom is 1400mm to the roof we would recommend 1200mm high units or even 1300mm units.
L2 H2 Transit Custom is 1650mm to the roof we would recommend 1200mm hight units - 1500mm tall units.
Take the measurement from the most protruding part of the bulk head (green dot) to the wheel arch box (yellow dot), allow 10mm minimum clearance. Use this measurement to determine how many standard units fit.
Transit Custom L1 H1 1100mm. What will fit? The diffrence between your measurement will be covered by a wheel arch unit, expained in step 3.
429mm + 429mm = 858mm
OR 629mm + 429mm = 1058mm
OR 474mm + 474mm = 948mm
Leaving off from step 2 we can now figure out how many wheel arch units will fit. (RED dot) showing were to measure upto, some vans have huge internal doors stops/hinges. These can be cut out the racking but might cut in to one shelf. Measure carefully and well with in the doors usually where the ply lining panel fits is a maximum.
If you require units on both sides of the van we offer slim depth units these can be found here Pro Unique Range
This increases the floor are between units mainly between the wheel arch's each side. All slim depth units are still able to take all standard boxes.
We also have a more in depth helper page for anything thats more custom that can be found here Van Configuration Helper