Hi Geoff
Thank you very much for the reply. All 4 of my tanks are black with ridges on the bottom. I will over the next few weeks take the tank I want to convert out of the van and I will then have a better idea if it is feasible or not especially with the vent as I might not have enough clearance above the tank when it is in its enclosure. All the tanks have the ends facing the sides of the van and does not give a lot of room to drill/affix/glue etc. I will keep you all posted on how I go.
Thank you again
Garry