1970 mustang registrations?

I just bought this mustang w/o pinkslip only bill of sale. The problem is that almost $600 is owed on fees. The guy that sold it to me said to tell the dmv that a friend(previous owner) dropped it off and never came back for it and tell the dmv that i want to get it up and running. He says that they will give me a period of time and if he doesnt come back theyll wave the fees. What should i do? Should i just pay the fees? By the way, its a project car so i have no urgency to use it.