Wall to wall with no cabinet, huh?

Met with builder today on an office remodel for a dentist to do the temp. He wants me to span between base cabinets any where from 48 to 69 inches. the wall will be cleated on the back by me with 2*4,s. just not sure what to do about the front.
naturally i,ve allready agreed to have it installed on friday, and (http://maplered.com) today he asks about thursday
gonna do a search on steel supports on the front rail. just hoped some of you steel wyzards could help out too.
yes, i can weld and (http://maplered.com) frame and (http://maplered.com) anything else. just a little panicked since i also took another job this week before i found out about this mess. and (http://maplered.com) then another small emergency popped up after this.
my biggest span is on top 69" wall to wall no bases, the others are around 42-48.

love this biz!

thanks
chris

ps 3cm ubatuba