The heel on a tiltback neck is the same as on a non-tiltback, so there is no difference as far as how it should join the body.

It seems to me the only case you'd need a shim or angled neck pocket would be if you had a bridge that sat higher on the body, like a tune-o-matic, floyd rose, or something of that nature.

Tiltbacks are cool - I mentioned to Tommy that they should make 2 standard pegheads - a 3 on a side and a straight 6.
There is a company called Fano Guitars that has a cool straight six tiltback. I was able to see one of them in person - nice guitars, but pricey for a bolt on. Here's a pic of their headstock:



IMO 3 on a side pegheads would look best on something like a Carved Top T or S body, some type of LP shape, or something like the Ibanez S Classic. I had one of those Ibanez's. It looked cool but the body was too thin. I like my guitars with some meat on them! ;)