I've kicked it around myself for my own project and after much thought I think glossy is fine and here's why... I believe we said there is no date restriction or timeline so you can claim it's, say, 1979. Would it be a shiny sleeper that year? Secondly, I remember clearly there was no fondness for Pacers then, no matter how shiny, it would not be looked upon with any particular admiring notice.
I'm going shiny on mine because even in the snow belt I haven't seen hardly any dull PTs. I say the more it looks like a family wagon, the less it will look like a street threat to anyone at all. I don't think junker is the only form of stealth.