Was it possible for a 327, 275hp car with a powerglide tranny to come from the factory with
a PC coded differential? My book says this was
for the 350/4 speed. Any known acceptation to this rule??? Like, if someone ordered this set up back in the day, could they have done so? Thanks

I beleive you could only get a 2.73, 3:08 or 3:55 axle with an L30/PG combination in 67. Don't know if special axle ratios were available for this combination but then again I own a 69.

Link to this site, click on top of page "diff and axles" this will give you what was available. http://www.camaro1stgeneration.com
I have an L30/PG with 3:36.

Yes, it was possible, I have one. Its a coupe though. My PC coded axle has a date of September 1966.