How about some pictures of what you've got, Bill?
Seems to me there are three options: (1) restore to original using replacement fiberglass pieces, (2) rebuild original configuration using wood cabinetry, or (3) keep the larger bed and make it look nice. With #1, shipping is the biggest obstacle. Option #2 requires decent cabinet-making skills to get something that is sturdy, lightweight, and well-integrated with the existing components. Can't say much about option #3 without seeing what you've got, but some people would find the larger bed worth a reduction in the size of the cabinets.
Before you invest too much in the cabinetry, make sure the floor and frame are sound. Floor rot and cracked frames are not uncommon in units that old. Don't want to build on a rotten foundation…