Since this thread got a kickstart from jools&jim, I'll post the updated list of books that could have a Marvel Pizzazz insert in them:
Marvel Pizzazz Inserts (41 total)
(All are from Jan.-April 1978)
Amazing Spider-Man 176,177,178,179
Captain America 217,218,219,220
Conan the Barbarian 47
Fantastic Four 190,191,192,193
Incredible Hulk 219,220,221,222
Invaders 24,25,26,27
Marvel Tales 87,88,89,90
Marvel Team-Up 65,66,67,68
Marvel Two-in-One 36,37,38,39
Star Wars 7,8,9,10
Thor 267,268,269,270
I believe I now have 23 of the 41 issues.