how much more work and what are the risks of going to a 393 over a 383? I tried a search already and didnt get a whole lot out of it .

Thanks Scott

 

Depending on the rods a small base cirlce cam will be required. 396 is more costly due to the crank as off the shelf 383 cranks are readily available. Most prefer 383 so you can rebuild and still have room left in the cylinder walls. Same thing goes for pistons as 396 are custom built to spec.
If you are looking to build a 396 in a couple of months I got a Forged Lunati Race Series crank 3.875", Lunati Pro mod I beam rods 5.85" Forged Ross pistons that I'll be taking out of my car. Parts are have less than 10K miles.

Good luck whatever route you decide to go.

 

There are plenty of off the shelf 396 parts and the overbore is the same as a 383, they do require more block clearancing and depending on what length rods the pin pushes the rings awefully far up on the piston which can be a problem with forced induction or juice though the parts are out there to make it work.

Still I would say just go with the 383, great balance of torque and HP little less block clearancing and most shops will be more comfortable with this common size.