The only bad thing about the DUI is that I dont think you can run the dist with the coil in it when you have a small block in an a body. I think there's a problem with firewall clearance.
That is possible; it's a pretty large distributor. I'm not aware of any small coil in cap designs, though.
I'm pretty sure the only difference between Magnum and non-Magnum distributors is the electronics (Magnum engines are crank triggered in stock form). If you're not running a Magnum computer, a non-Magnum distributor should work from what I've seen.