I know you can't fight City Hall, or more specifically Sacramento- since I'm not going anywhere and my customers often request this type of work it's in my best interests to become proficient in making 76 and later T/A's and Firebirds smog compliant. It's more work of course, but I have no problems with doing the work or complying with the emissions laws - it just takes time to do it right. And we're dealing with 30+ year-old cars here- if the fuel system or exhaust isn't 100% the car won't pass.
Older vehicles sometimes with high mileage sometimes have a harder time passing emissions testing, so even after all of the appropriate work is done they sometimes don't pass. Extensive tuning is often needed, which only works on an engine that still has good seals, proper clearances, and good compression. If you're swapping in a used motor with unknown history and condition, there are no guarantees- it may even need an minor overhaul to make it run decent. It's very unrealistic to expect a tired old motor to run like a new one and still run clean.
Knowing what I know now I don't have alot of big concerns getting my '76 T/A smogged and certified when the time comes, but as for the '78 Firebird, that remains to be seen, since the owner wants a used motor.
Geno