It's quite hard to see on a pic, but if you look at the pickup rings on many, many bursts you'll see that they are flat, not bended like a modern les paul. If I may quote John Catto from another forum regarding the top carve:

"That's how it should be. Curved decks are for production standards and Historics with a lousy top carve

Joking aside it's surprising how flat the late 50's guitars can be. Check out this pic, at the bridge pickup it's dead flat and extends as such well past the pickup rings, at the neck it has just the faintest whiff of a curve on the bridge side which is accented just a bit by the ring shrinking and pulling up."

The pic John talks about is missing so I'm showing you this instead. If you look at the pickup rings you'll see that they actually are flat.