Also- if the label is gone from your 29-year-old truck, check in an
Emission Control Guide, published by Chilton's and others, mostly
likely on the shelf in your local library, or any state-certified
garage or inspector has to have one (or online guide) on hand, they
might look it up for ya if ya ask real nice... Have your VIN in hand,
with the guide you'll know exactly how that vehicle was equipped (or
should have been) when new.  That's what CA will require.

If it has aftermarket accessories, (like headers, cam, carb) check with
the manufacturers of those items to see if CARB-approved.  If so, they
can give you a sticker that has to be displayed under the hood to pass
inspection.  If not, you're SOL, get it outa there.

If your truck has been de-smogged, well...  Finding all that's missing
may be cost-prohibitive, or at least a big pain in the a.s, compared to
just replacing da big-block 'Charger with something that will pass,
unless you're completely in love with the thing.  Or get an earlier one
if you can find one- 1975 or older are exempt.

If you're moving to CA, and your truck is equipped OEM, and you're not
sure if it'll pass, find out from CA DMV what the acceptable levels (of
CO, HC, NOx, I think that's it) are, take your truck to a shop with a
gas analyzer, have them tune it into spec if it isn't already.  If they
can't get it within spec, something's wrong and needs fixing.  To pass,
it has to be within spec AND originally equipped.

Be sure timing is correct and use new plugs, cap rotor, and wires for
the test!  These items are the cause of most smog failures, usually not
the smog equipment itself.  If originally equipped and everything's
working properly, it should pass just fine.

Oh and one more thing, if the engine is not original, don't despair, it
could still be legal.
This is how it is in Nevada, I'm told it's the same in CA.  It has to
be the same year or newer.  To prove this, you need an affidavit from a
manufacturer's rep (a dealer) identifying the engine (by its numbers)
and what vehicle it came out of.  The engine has to be as equipped as
it was in THAT vehicle. The DMV lab has to do the initial inspection,
though renewals can be done anywhere.  Finally, (duh) it has to pass at
the tailpipe.

For more info:
http://www.dmv.ca.gov/vr/smogfaq.htm#BM2536
http://www.arb.ca.gov/homepage.htm

I had a heck of a time and a lot of junkyard searching to bring my
de-smogged 1987 carbureted Toyota 4x4 back to NV-legal (sigh, I was in
love.), something I wouldn't do again.

Of course, you could just swap the VIN plate for a '75.
BUT THAT WOULD BE ILLEGAL!!!