Is all that compatible with a plastic fuel tank and stock fuel lines?
I don't know for sure, but I'm fairly sure the paint would be OK. Most folks brush it on instead of spraying, so you could avoid contact with things you don't need coated. The stuff CR was talking about come in a plastic spray bottle (at least what I have used in the past has.....some may brush on) so if you are careful, you could keep it off certain areas.
It can be used on a variety of surfaces, from styrofoam to wood to concrete...I would think it would be OK on plastic, but wouldn't hurt to shoot 'em an email to verify.
My friend used to do complete frame-off restorations of 60's era British Land Rovers and he used the Por15 to coat the frames and suspension parts.
http://www.por15.com/POR-15-Technical-Information_ep_62.html