1978 Mongoose Motomag

I just picked this up at the local Goodwill Store 99 cent sale (flat tires and all, but I thought 99 cents was a steal :-). I have not done anything to it yet. Frame serial numbers indicate it to be a January 1978 Mongoose. It has the coaster brake tab on it. Paint is scuffed a bit, but bike looks pretty good to be 30 years old this month.I believe somewhere in it's life parts have been changed / upgraded.