[Mg-t] positive ground

[oliver]

just picked up a 52 td last week.

sat in a garage 30  years.  the dpo put a battery in it, and this weekend we 
got it running.

am a little concerned, tho, because the battery is in standard position, and 
the car should be positive ground.

is there a way to tell if it was ever converted to negative ground?
would it start and run if the battery was in backwards?
what should i do at this point?
i wouldn't mind having it positive ground.