Just found a small excerpt for you from an article on cichlid-forum.com.
"In the wild, frontosa live in large groups called colonies. In the aquarium, they should also be kept in larger groups, although they can be kept successfully in groups as small as four individuals (1 male:3 females). You'll have the best luck keeping only one adult male, and if your colony is larger, a second, subdominant male who will eventually replace the alpha-male. If you're growing your Fronts up, the "best" method is to acquire 12-15 individuals (all unrelated and from the same race) and put them in a tank of their own."
At 12-14" adult size, a group of 4 (3 female, 1 male) would likely need a 125 minimum as rbishop mentioned above. To house a "colony" of them, supposing at least 10, you're probably looking at a 200+ gallon tank. Despite their small size now, they will grow rapidly, so I wouldn't suggest getting them if you plan to house them in a small tank and purchase a new one "once they've grown into it." Not assuming you will, just a common thing to mention.
Edit: Just noticed that you aimed to keep them in a 60. Though they will technically fit for now, they will quite rapidly outgrow that size tank. Using it as an "excuse" to get a bigger tank is unfair to the fish... all the time necessary to locate all components, assemble, and cycle the larger tank may take 1-4 months, which may leave them in very cramped conditions. Perhaps a different type of cichlid would be more appropriate for your 60 until you can afford to start a 150+ specifically for the frontosas?