I have a 350 vortec and want to change the stock cam. A hydraulic roller seems nice .500 lift. If I do this will I have to dress the heads up? If so what does that consist of as far as the specs? As for the carb 650 double pumper good or maybe 750? Thanks for any help.  

So you don't have a fact. roller? You can take your heads to a machine shop for screw-in studs and spring setup from whatever complete camkit you choose.     WIEDER  

Depending on the springs recommended by the camshaft manufacturer the spring pad on the heads may have to be enlarged. Regardless of the spring's outside diameter the guide boss must be machined for a smaller O.D. valve seal and possibly be reduced in height to eliminate retainer to valve seal clearance issues that plague vortec heads (this is the reason why stock vortecs can't physically accept more than .420" lift).

These valve train mods and "setup" are usually best left to a machinist even though if you do your research and order the parts and cutting tools it can be done yourself.  

Yes I have the stock Cam. The machine work will be done in the shop. Since I want to build this with a bigger Cam what would be my best bet? If Iam right .500" is the biggest I could go, but maybe bigger in this case bigger may not be better?  

Thanks for the help as well just gettind started with this. This is my first build or engine if you will.  

A half-inch of lift is usually a good amount for a street machine that will be fairly durable with a flat tappet. Getting to .600" with a flat tappet is rough territory, and the consequent duration at that lift figure would require a lot of compression, low gears, and a loose converter, all things that are not favorable to a street car.

You are going to need to determine how wild your cam is going to be so you can at least get the specs of the recommended valve spring so you have some idea what needs to be done to the heads.  

Ok now understanding I think the .420" is the way to go for now intill I have more knowlege and money. So you say that is the way to go to keep it all stock without changing anything?