Tank/light combo.. would this work?

Okay, I am looking at buying a 100gal tank as my first SW tank. I want to go reef, but will only be doing the hardiest of corals(shrooms, eventually zoanthids). Do you think I would have sufficient light in a 60" x 18" x 18" tank for those if I used a 48" fixture or would I have to go 60"?(and not place corals on the ends of the tank) The lighting for a 60" fixture is what is holding me back. I can find appropriate t5 or MH lighting for 48" cheap here in town but 60" lighting is quite a bit more.

So I guess the question is... should I stick to a 80 or 90gal tank and go with 48" lighting or can I bump the tank length up and keep 48" lighting?

Thanks for the quick reply. I just found a killer deal on a 100gal tank/stand(assuming they are in good condition), and I would love the slightly larger footprint of the tank. I guess I'll go ahead and take a peek at the tank and see what happens