12v slide out step (1 Viewer)

[gramps]

Hi first time on the forum and need some help.
We have a 2053 fiat ducato the problem is i need to fit a thule 400 12v slide out step on n/s cab door [we're getting old]. i've been told the v18 and will need a fixing kit at £70 will it fit my van and if so how dose it fit dose it fix to the sill. Is there a differance between the v16 and the v18
I will be grateful for any help

thank you