i have the chance to buy a 66 mustang coupefor $200it has a I6 with factory air and it runs but its pretty rough. the guy says he has most the parts to fix it. it has good interor but is missing the back seat. he says the floor is getting pretty rusty but i havent looked under it yet. now if i did this i would most likely do a engine swap havent decided what but would this be wrong? how hard is a floor pan to put in? is a back seat expensive? would like to hear your oppinion.