Thanks for the detailed responses. When I do my 56 Dodge pickup onto my 2001 Dakota donor frame/floorpan/firewall I may clean and repaint the bottom side of the floorpan, then coat it with pickup bed liner product. Then use some of the products mentioned above to do all the seams, corners, crevices etc to let it creep/seep into those areas. Do either products give off any kind ot smell? I am very tolerant to the usual automotive smells, bodywork smells, fiberglass, etc. My wife, err not much at all.