Stock D3 Heads

Im building a dragster for my son who just got finished with 4 years in a Jr Dragster.  

Its a 235 wb,  will probably weigh about 1900lbs  ( im guessing) with the stock 460, D3 headed motor and stock cast iron intake.

Powerglide with a 8 inch ATI converter,  

I don't want to scare him with a high horsepower motor so Im dropping in a stock motor to start.

Im going through this stock 460,  and I would like to put in a larger cam.
The cam in it now doesn't look too healthy, so to be safe, Im just going to throw in a new cam.

Because of the stock D3 heads,  and non-adjustable rockers, Im guessing that Im limited in how much lift i can put in.
From what I have read so far,  I'm limited to about .540 lift...   I think???

I dont want to put any money into the heads except using the correct springs, retainers, keepers, etc.
But Im going to leave the stock rockers on.

Any ideas on which cam would be a good one?

You are correct about the lift...
  A custom hydraulic lifter camshaft using the correct, matching components in the valve train with only that amount of lift but, duration to match the vehicle and torque converter is your best bet.

I was thinking about Comp Cams 34-331-4,  Magnum 280H

Anyone have any thoughts?

Its hard to pick a camshaft for this application,  lol

With an 8" converter ... that is not a good choice; not even close.

I'd swap a set of early heads on it to at leash give it a little snap.

I understand,

All i was trying to do was find something a little better than what was in there.

And not have to feel like i was pulling teeth to get an answer.

As long as it starts and drives,  its ok with me.

A stock 460 should have this thing in the high tens in the 1/4.

So coming from a Jr Dragster,  which runs like mid 12's in the 1/4  to this car,
I wanted to make sure he could handle the car,  And then build a better motor.

This engine will only be in until I can build his new one. 
Which should take me a month or so.

I hope I've done this right,,

Here is a pic of the project so far.

It doesn't sound as if you understand at all.
An 8" converter will have a stall speed somewhere up in the 4,800 RPM range pr higher but, you wish to use a cam which is all done at 5,500 RPM; IF even that high when used with other stock components. It definitely will start and run so, go have a good time very slow.

Use an 11" converter around 2,800 to 3,200 RPM stall speed and MAYBE it will be OK.