casting number 906 with screw in studs and guide plate....got from moose5.7 on here....lil bit rusty....is the casting worth having vatted and rebuilt?

Definitely.

For sure - those are the much talked about 'Vortec' heads (906 and 062 are the two desireable castings). Get them crack checked first, as you should with any used heads/crank/block, then defietely have them machined for screw-in studs, guideplates, and valve guides cut to handle more valve lift (stock limit is about .450" lift).

i guess i lucked up cause they have screw in studs and push rod guide plates....i thought that was factory for newer heads.....anybody know a good cam for those heads and an air gap intake?

Not to sound like a broken record (although this recommendation is getting old) the xe268h and xe274h are both proven performers with vortec heads and a performer RPM /air gap intake.
Stall speed needs to be upgraded in the torque converter.

i have a 2600 stall......hows the idle on those cams? i had a big blue racer in the engine before and it would rock you out of the car on idle....im lookin for somthin with a smoother idle.....you can feel the engine running, but it doesnt feel like you have solid engine mounts either, you know what i mean?

I've got the XE274 in my 350 (but with different heads) and its got a pretty nice idle - its got a fair bit of 'lump' to it, but its not really racy sounding either. Sounds great IMO.