To the letter of the Clean Air Act of the late 60's, unless it has CARB or EO status, your dead. Down with legalistic hammer, and take the man out to the stocks for stoning. Thank goodness most states have there own ideas!
Cam
The general concensous (sp) is 270 degrees and about 0.26 * the maximum valve size in lift.Thats about 455 thou at the valve for a 1.75 intake. The critical part is the amount of degrees both valves are 30 thou open at the same time. This allows for quite savage opening rates that the get blunted off as the cam rises. Quite often , the 50 thou duration figures aren't very big on these cams.
Any standard 270 or so grind will most likely be set up with autos in mind, and these cams are good for emissions engines.
The plus is these cams make excellent torque, and thats what rules n the streets.
Work has been done with custom billets on differnt lobe centres for emmisions engines.
Visual and Sniffer Tests-what Iv've read
We all know the smog dawgs can bite hard if your 25 year old EGR, air-pump or PCV or thermostatic air valve isn't there, but these items really do improve cold starting. Most pollution is on start-up, and after that its just a matter of engine tunning. Many drivablity problems happen when items placed on the car as a development requirement from engineers in testing labs at Ford get thrown away, or loose servicablity. Often, a spike of alcohol or retarding the cam or ignition will help give you room if this is the case, but the real issue is its often impossible to get the exact replacement parts.
The advances over the last 25 years have been in cold start warming of the engine, and in using better fuel systems. These don't need as much heat as the 144-250 engines put into the intake manifold. I think Mark P related that the heat stove is a power waster after warm up, but that the EGR is not a problem. Fuel has gotten lighter since the heavy metal days of hi-test Sunoco or even the old regular gas.The oxygenates, extra alcohol and aromatics cause hot fuel handling problems these days with it.
They do, however, further lean-out the mixture. So the idle Co and Nox and HC standards in 1976 should be easily met.
There is lots of freedom to raise the compression by decking the block, using later larger chamber heads with HSC Tempo pistons, and using the Clifford port divider. The chamber and Fords gaskets were most likely designed around a blueprinted engine, but Ford had crazy wide production tollerances with respect to pistons, rods and deck height. All this doesn't change emissions if you are moderate in your mods. The exhast could be changed for a later type too, as long as the visual inspection is covered off. I think a better emissions area 2-bbl Holley Weber may be used if it has been benchmarked with a known combo. As long as its all tamper-proof and jetted right.
According to a Hot Rod article way back in 88, as long as the visual and sniffer test comply, then its okay to bechmark a stock 1-bbl car with the modification as long as theres no difference in any tailpipe emissions. What the Smog Dawgs get snarky over is the attitude that she'll be right. If you have gone some way to getting parts that have smog certification on other cars, retro fitting can't be a bad thing. There's lots of Pintos, Fairmont 2.3's and Fox stangs and Capri 2.6/2.8's to snatch Holley Webers or Motorcraft emmissions era carbs off. The ignition set-ups are another area. The vaccum advance units are not always compatiable, but if you use later emmissions spec ignitions, then you must win browny points.