t5 seats in t4

Been looking for the right thread but can't find the answer; I have a T4 2000 SWB and want to change from the single passenger seat that came with the van back to a double, prefer the T5 seats and have been told they will fit with either a bit of drilling or replacing of the seat base but can't...

After sorting out a few minor issues with my T4 syncro caravelle the Steves pulled a blinder and fitted a triple rear T5 caravelle seat with the four full length rails in the back. I now have a sweet leather three seater that slides pretty much the length of the van with three three point...