Plymouth Gold Duster

I am looking for opinions on the sale price/value of a 1974 Plymouth Gold Duster. The seller says its a 318 with a 727 auto trans. (I seem to think it isn't a 727 but if it is when I look at it... yay!) Any way the seller is asking $4500, i think that is a bit high because,from the pics the car looks to be repainted with rust issues on the A pillar and around the windshield. I suspect the car had the vinyl top that started part way up from the rear window and went down the A pillars to the cowl. I don't know or wont know if the car "needs a roof" unless I buy it and start stripping etc. So, two questions, what would you guys offer, and what rear should be in it? ( I am thinking the 8 1/4 rear probably not Sure grip). I beleive the car runs drives and stops. I was thinking $3500-$3800 first offer, then probably end up around $4000 ( If I dont offend the guy) :).