I have searched the entire KCMO area, and found exactly 2 cars, both with not a lot good on them. I have called salvage yards for days, and have come to the conclusion that they are too old for most yards to have, yet too new and undesirable for classic yards to have. Kind of stuck in the middle somewhere. Looking for front wheel well moldings for a woodgrain car, one upper quarter panel trim piece and a better set of tailgate hinges since the '79's were apparently a one year design that suck... If anybody has anything, a car they're parting, or knows of one in a yard within a days drive of Kansas City, I would greatly appreciate it! Could also come from a Mercury Colony Park, will be refinishing the trim anyway, so finish isn't important.
Have you been on crownvic.net or grandmarq.net? Grandmarq.net used to cater more to the 79-91 boxes, whereas crownvic.net seemed to be more aero and whale oriented. I haven't been in either board in years, but I'm sure there are resources there. Parts are still out there for these, but yes, most of the self serve junkyards these days are devoid of much over 15-20 years old.
I was just at two big yards in South San Antonio, and one had a few box Panthers, but zero wagons. Try Row52 just to see if any yards that participate nationwide have what you're looking for.
The last wagon I saw was at Pick 'n' Pull in Lynnwood, WA last summer, but no telling if it's still there or not.