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How does a 403 with .020 over pistons and #6 heads and the cam above sound? How much hp and torque would it make etc...

 

One must be mindful of trans and rear gear ratio when picking a cam. That cam appears to have 67 W30 and 68 W31 specs. The factory designed that cam for forced air induction, minimum 355 rear gear and I would suggest a higher stall speed converter if auto trans equipped. It has a nice sounding idle as well.

 

I'm no cam expert but it doesn't look like a good cam to me. I would figure out what your goals are, what CR and gears you'll be running, then pick out a better one that will work with that.

 

im guessing the gears are three something posi for a 79 T/A.

 

When planning out an engine build, guessing is a sure way to end up with something that may very well not perform up to your expectations. Either way, I don't think that's a cam you're going to be happy with.

 

Maybe 500?

You didn't tell us which piston, ported heads, intake, carb, nothing else.

See my point? More info is needed.
And don't guess on your gears. I'll bet they're in the high 2's but find out for sure.

 

I had a stock 403, and with some bolt ons, thing ran pretty strong. Was/is a place in CA called HO Industries that used to sell all kind of parts for these engines, and what I did. I used their custom ground cam, Q-Jet rejetting kit, dizzy recurve kit, and got a 3.73 posi rear axle, and was quite a threat on the street, until I broke it, with what sounded like a bad rod bearing. I just built a stong 455, and switched them out. Had the 403 on a stand for awhile, then later checked it out. Rod bearings were all fine, so figured it was frozen piston pin. Later sold the engine to a friend, and sat for couple more years. He finally got around to doing something with it, then called me asking what was wrong with it, as ran fine, with no rod knock. He did nothing further, other than dropping it in a 70' F-85 post coupe, and still lives on today. Pretty nice install too, as sent me some pictures.

 

You have high 8 to 1 compression, unless the block or heads were milled with cast pistons. Most 403 Trans Am's supposedly had 2.56 or 2.73 gears. Go much milder duration wise and add 3.23 gears.

 

It will have a fairly rough idle, good power over about 2750 rpm. It would be a better choice with headers and rear end gears. Even then, you might do better with a newer grind with quicker ramps, like an extreme energy from Comp, or similar from someone else.