I am considering adding more HP. I have an 80 L82, valve job last year, has true duals, carb jetted by LARS, tuned 36 advanced, runs strong. Originally was 230HP.

If I add vortec heads and an Eldebrock performer intake what should I expect HP to be?

FLA VETTE38577.7481828704

Depends on what the final compression might be.  In most cases I have seen about 20 HP for each 1/2 point of compression on stock type or slightly better heads.  If the heads are a whole lot better then you can bet 30 to 40 HP.  Cam selection will be very important to take advantage of any head upgrade.  Not sure if that answers your question or not, but its a good basis to begin with.

Intake manifolds can be worth 15 to 40 HP.  Our new Weiand vortec intake that we just dynoed made 25 more HP and 25 more ft lbs then the edelbrock piece on the same engine.

Picking the right parts can be critical because they must all work in harmony to be effective.

Actually, let me ask this a different way. Car runs pretty strong but I would like more low end torque (fun factor).... rear gears? From what I have read, the L82 cam is supposed to be a fairly good cam (not sure if this is a wear out item at this age - 100K miles). I am not a mechanic so I am trying to pick mods that I might be able to handle my self. I am trying to figure if it is worth changing the heads since I had a professional valve job done last year. If the gain is minimal, I would most likely leave it. The intake change seems to be worth doing from what I have read. I was looking at all these great crate options availible to get 350+ HP in some of the recent magazines but I would like to use the engine that I have to get there if I can figure how to get good gains in performance. That also keeps me from having to store the numbers matching engine. If I can't get reasonable gains, I may consider having a pro pull the engine and build it but I hear that is as expensive as putting in a crate engine. ...options......????