I would like to repaint my van and want to be able to get the seams of the panels filled but what is the stuff they use? Also the guttering where the hightop is fixed, what is the sealant they use?
The equivalent stuff used at the time in this country would have been 'Drip check' seam sealer.
The modern day stuff is more of an adhesive sealer which does what it says on the tin (Sticks and seals) it is used for a multitude of applications from gluing panels on to vehicles to covering a bit of a bodge, trade name of one brand is Sikaflex .
Any of the polyurethane sealers such as Silkaflex etc work well.
I get mine from Toolstation as it half the price £3.66 a tube, Screwfix used to do it for around the same price but it seams to have dropped out of their catalogue.