is a 383 stoker kit worth it? what do you have to do?

 

There's no replacement for displacement, as the old saying goes.

As far as what you have to do...

Basically you need to have the block machined to accept the new components. It will need to be clearanced for the extra stroke and then all your other standard machine work that's involved when building a motor. You could also splay the main caps for extra insurance. And, you really should have the heads reworked or else you will starve your new bigger engine.