78 rpm speed for Thorens?

With a modern moving iron cartridge in the 200-300 dollar range is it a safe bet to be using it in the 78 rpm speed mode? Is there another cart that I should be using for 78's?
You should use a cartridge specifically designed for 78s; the grooves on 78s are considerably wider than LPs and require a much wider stylus. Check out 78 forums on Vinyl Engine and Audio Asylum for more info.
You could check to see if you can get a 78 rpm stylus for a cartridge you may already have.