According to the 4/29/79 timetable, the Floridian would leave Chicago at 9 PM on day 1, and arrive in Miami at 1:10 PM on day 3. A bit less than 40 hours to get there. It now, going CHI to WAS, takes 46, via the Capitol Limited and Silver Meteor.
Now then, we can honestly come close to that time, say 40.5 hours, creating a tri-weekly "Floridian" running CHI-WAS-MIA with 3 P42s, 3 CCCs, 3 Trans/dorms, 4 sleepers, 4 coaches, and 4 coach baggages. Here's how it works. The Capitol Limited on those three days runs P42, Transdorm, 2 WAS sleepers, CCC/Diner, SSL, 3 WAS coaches, 2 FL coaches, 1 FL sleeper. At Washington, the CL breaks up short of the station, decoupling the 2 coaches and one sleeper, then pulls itself into the station. A single P42, coupled to to a CCC and Trans/Dorm, backs up to the other 3 cars, couples, then pulls into WAS. It then leaves shortly along the Silver Meteor route.
The train gets to MIA, and turns for the next day. The train then goes back to WAS, uncouples its CCC and P42, and gets reattached to the CL. In essence, the three CCCs and Trans/Dorms short turn in WAS. For servicing, they could be rotated into the CL.