24X4 is 96 pins, which would mean 48 to a side in a DIP. 48 pins x .1" pin spacing is a 4.8" long chip. Thats a little teeny bit impractical.
Like dxw00d says, if your looking for dip horsepower, look into the 1284 chip, its not quite the 2560, but its got more memory and pins then a regular arduino (and crossroads makes a board for it, I don't have one, but my friend does, and he loves the thing)
On the other hand, if you just need more pins, it might be easier to just use a couple 328 chips, each doing part of your project, and then having them send necessary data between eachother (done it a bunch of times, esp for the projects where I'm lazy and just wanna make 1 sketch to only do like 2 things but then want to expand on it without having to shove a whole lot more into the code)
-edit. Heh on looking at crossroads website. He makes a board for dual 328s too.