You do not need a framing structure for a cage that size. You might consider some sort of central support in the center of the door, but that's it.
You should look at the cage plans page at AlbinoBurmese.com?
I would not use solid oak for the cage, if that's what you mean. I might consider using oak-laminated plywood. Plywood is much more dimensionaly stable than solid wood, especially with the temperature and humidity differences a snake cage experiences inside and out.
If you use melamine I strongly suggest you get the cabinet quality stuff from a cabinet supply store or a lumber specialty store. The melamine coating is much more durable than the stuff from Home Depot, Lowes, etc. stores.
Another possibility is to build the cages from hollow core doors. Again, I'd try to find a higher quality door if you can. An individual door is 80" x 24", which is only 6" longer than what you've planned on. For the sides you can cut up a single door like you see in the rack plans at RioBravoReptiles.com.
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Current snakes:
1.1 Gonyosoma oxycephala - (Silver/Yellow)
2.2 Gonyosoma oxycephala - (Green)
4.3 Gonyosoma janseni - (Black)