For years I’ve looked in Bouscaren, Prummer, and other texts, nothing.

I looked again at Jone and Woywod, still nothing. Does anyone have a reliable source for this “turkey indult”?

QVD:  I'm not sure what you need here, but the links provided in the OP come from here:

http://www.clsadb.com/search/?q=Thanksgiving&volume=_&order=relevance&page=4&take=20

#63 provides the reference book, etc.

My last post on this unless new information comes to fruition. I call it hearsay, there is absolutely no proof, that I am aware of, that there was an indult for the Friday after Thanksgiving. The day after Thanksgiving is not the civil holiday. I have seen proof for a Fourth of July indult, but never for Thanksgiving.

Could this newChurch tradition be similar in legal standing to Paul VI’s cremation indult?

… it seems like all too often whenever penance actually becomes penitential, people want a dispensation from it.

This question comes up every year, with plenty of verification that a dispensation was granted.  Whether that dispensation is applicable to traditionalists today (since His Holiness Pius XII is not the current pontiff) may be another question.
It is a source of bemusement as to why there is always so much hand wringing over this.  If one has doubts simply leave the turkey in the refrigerator until Saturday, it seems simple enough.  That is hardly penitential when one can have lobster, crab cakes, salmon (I'll eat salmon over turkey any day), clam chowder, fish and chips, or made from scratch mac & cheese (made with a very sharp cheddar).

This question comes up every year, with plenty of verification that a dispensation was granted.  Whether that dispensation is applicable to traditionalists today (since His Holiness Pius XII is not the current pontiff) may be another question.
It is a source of bemusement as to why there is always so much hand wringing over this.  

I think I was probably one of the first to publicly question -then doubt- the existence of this indult (for about the last 4-5 years), until the link in the OP was shown to me on another forum.

After that, I no longer question its existence, and am not sure why QVD continued to.

That said, whether or not the indult was a prudent dispensation is certainly open to question, and of course people will disagree here.

Personally, I found it unnecessary and worldly, but...

I guess a question which I am still unclear on is whether the indult was limited to turkey, or is all meat permissible (eg., what about American families who have ham or other meats?  Can they have that on Friday too?)?

In any case, I think for most trads, an indult for eating meat on a Friday following a merely civil holiday would leave one feeling a bit uneasy (not because there would be sin, but because of the worldly motives which inspired the indult).

It seems the indult was part of a larger trend of worldly American laxist disciplinary norms (eg., the pre-conciliar trad world mocked American norms for Lent, where most of the rest of the world practiced daily fast and abstinence, but Americans only fast and partial abstinence).

In any case, I think for most trads, an indult for eating meat on a Friday following a merely civil holiday would leave one feeling a bit uneasy (not because there would be sin, but because of the worldly motives which inspired the indult).

It seems the indult was part of a larger trend of worldly American laxist disciplinary norms (eg., the pre-conciliar trad world mocked American norms for Lent, where most of the rest of the world practiced daily fast and abstinence, but Americans only fast and partial abstinence).

Yes, it does seem like the indult had worldly motives. The Federal Government put Thanksgiving on a Thursday and not on a Friday so that Catholics can eat the meat, yet some Catholics wanted more. I wonder what group of Catholics, that had such a love for turkey so much that they could no longer wait one day to eat it again, that they had to ask the bishops for an indult.

It's not about the meat, but rather about allowing for the entire weekend to be festive, rather than immediately tempering it with a penitential day.  Everybody's making too big a deal about this.

Sure, but if Mr. G is correct that the Masonic US government really scheduled the civil holiday on Thursday so Catholics could participate, then it means that even they had an expectation that the holiday was a one-day event, and that on Friday Catholics would not eat meat.

And if secular America later transformed Thanksgiving into a 4-day bacchanalia (despite having more food/menu items than anywhere else in the world), it would seem the Catholic hierarchy was following their lead.