[super_kit_car]

I have a 85 street mustang with a 472 tunnel ram engine, I like the comp cam magnum 306 solid. depending on how you will be driving the car determines what is the best choice for your rear axle ratio. with the C-6 and no overdrive I would use 3:73s , with a 27 inch tall tire, at 60mph you should be running about 2700-3000 rpms. you don't want run your engine at anything over that range for an extended period of time, I'd say no more than an hour's ride would be safe, anything over that you would be better suited using the 3:55s or lower, again depending on how far you drive your car. a taller tire also helps with you top speed. say the same combination above, the 3:73s and a 27 in. tire, you changed the tire to a 29 in. tall tire, it would drop your rpms to about 2500 at 60 mph. hope this info helps