Yeah both marvel and dc came up with the crusaders in joke and had them out the same month. Back when marvel and dc did stuff like that. They did a "crossover" in a issue of aquaman and sub-mariner in the same month also where the plot started in one book and ended in the other!
Kind of wish marvel would use ghost girl more. They did use dyna-mite more later when he became the new destroyer in invaders.
Invaders #14-15 were cover-dated March and April of 1977.
Freedom Fighters #7 (where The Crusaders showed up on the very last page) was cover-dated March-April 1977, but the actual meeting with the Freedom Fighters (in issues #8 and #9) was in issues with cover-dates of May-June 1977 and July-August 1977, so it didn't actually happen in the same month(s) as Marvel's Crusaders 2-parter.
By the way, some other people worth mentioning here:
They weren't created until the early 1960s, but they had many adventures set in WWII that crossed paths with Captain America and other heroes of the day.
In fact, they even met up with Heinrich Zemo (who went by the name "Dr. Zemo" at the time) before that unfortunate mask-thing and his identifying himself as "Baron Zemo".
Another interesting one from Roy Thomas back on his Avengers run in the early 1970s with the Kree.
While there was this in Avengers #97 (March 1972):
A few months earlier there was this in Avengers #92 (September 1971):
which appeared to include quite a few Golden Age heroes that weren't from Timely/Marvel.
(The one I'm not 100% sure about is the one just below and to the right of Captain America, though I'm guessing that might be the Fantom of the Fair from Centaur.)
Starting with the figure in the Top Left of that panel,
it looks like we have
Cat-Man (David Merrywether), originally published in the 1940s by various comic book companies under Temerson and then Holyoke.
He and his partner, Kitten, later became public domain properties and were used by both AC Comics (FemForce and others) as well as Dynamite (as part of Project Superpowers).
Also from that panel in Avengers #92 (September 1971), further down on the left and towards the middle (just below Namor)
we appear to have
Fighting Yank (Bruce Carter III), originally published by Better/ Standard/ Nedor comics. And as with Cat-Man, Fighting Yank later became a public domain character and was used by both AC Comics (in FemForce) as well as Dynamite (also as part of Project Superpowers).
However, Fighting Yank also looks like he may have inspired a character that did later appear in The Invaders:
Spirit of '76.
I thought it was an early Man-Thing drawing, even though Man-Thing was not yet out.
Marvel's Heap http://www.marvunapp.com/Appendix4/heaphillmanaveng.htm
I think it's pushing it to refer to the character as "Marvel's Heap" since the character was created by Hillman in the Golden Age and that version is who would have been referenced by Roy Thomas along with the other characters in that panel. Any incorporation/retcon of The Heap/von Emmelman into Marvel's past would have probably been after that panel was published and based more on any theoretical public domain status at the time.