Well, I'd start off with this Model Power coach, For the second from the top car)
ATSF-T COACH<br>No.5505 - 5505 and sand down the wood detail, then use .10 styrene, and make rivet lines according to drawings, add the scissors hand railing on the vestibules, then cut an appropriate sized hold in the roof, and scratchbuild the coupola, according to the drawings. If you want I can a painted and detailed interior, seats, and people too.
For the Top one, I'd scratchbuild out of styrene completely with grandt line doors, and have it ride on modified bachmann trucks.
For the Third one, I'd do just about the same thing.
For the Diesel, I'd either find an HOn3 Brass one, and splice 2 Bachamann DCC-equipped GE70tonners together for the drive, or I'd carve a body buck out of wood, milling out most of the interior, then cladding it in thin metal, soldering it together as I go along, then adding windows and a boatload of detail parts.
E-mail me if you're interested, this would be a fun project.
the(at)weatheringman.com <-My e-mail (replace (at with @)