You cant do it, well you could BUT
They will be like rolling on 4 flat tires
The sidewalls will be so huge and floppy it will not be good. I have 245/50/16's on an 8" rim and they seem floppy. I am going to downsize to a 225. You have a 6" rim on the stock 14's and are thinking of running 60 seris, trust me man, it will make the car handle like crap. The biggest tire you should even think about is a 225 on the 6" rim. I am sure you will get a lot of people saying the same thing.
------------------
85GT 2.9 4spd
www.david.westcoastfieros.com