Avengers #102 and #79 - Quicksilver and Vision Back to Back

1970: Avengers #79  J. Buscema

1972: Avengers #102 Buckler

Avengers #102 and #76 - Arkon and Vision Back to Back

1970: Avengers #76 J. Buscema 1972: Avengers #102 Rich Buckler

Avengers #102 and #58 - Double Vision

(Top) 1968: Avengers #58 - John Buscema
(Bottom) 1972: Avengers #102 - Rich Buckler

Another angle.

                              1968: Avengers #58 - Buscema           1972: Avengers #102 - Buckler                                           

Avengers #102 and #79 - Don't Fear the Grim Reaper

Classic Grim Reaper

(Top) 1970:  Avengers #79 - John Buscema

(Bottom) 1972: Avengers #102 - Rich Buckler

Avengers #101 and #56 - Captain America to the Rescue

(Top) 1968 - Avengers #56  John Buscema
(Bottom) 1972 - Avengers #101 Rich Buckler

Update!
In response to Silver Fox's comment, here's a Kirby image that I'd stumbled on some time ago. It's from Captain America #105 (1968) and when I first saw it I was immediately reminded of Avengers #56 (and by extension #101). However I think the lead time is just too short between Cap #105 and Avengers #56 (the Cap issue was on sale a mere month before the Avengers comic); I doubt Buscema had access to this image. Besides, it's a fairly standard composition. 

Anyway, here's the Kirby image from Cap #105:  

1968: Captain America #105  Jack Kirby

Behold the Vision! Avengers #57 and Marvel Two-In-One #39

Classic Vision stance! First, Vizh flexing some muscle in his debut in Avengers #57-- by Big John, natch...

1968: Avengers #57 - John Buscema 

...and here's Vizh in Marvel Two-In-One #39--Ron Wilson's version.

1978: Marvel Two-In-One #39 - Ron Wilson

The full Buscema panel from #57.

1968: Avengers #57

Avengers #59 and #362:John Buscema Master Class

Avengers #59    J. Buscema                                                                         Avengers #362    G. Purcell   

Giant-Size Avengers #1 (Pt 59) Iron Man and Nuklo

1966: Tales to Astonish #82 Kirby

1974: Giant-Size Avengers #1 Buckler

Giant-Size Avengers #1 (Pt 58) Vison, Nuklo and Ben Grimm

1974: Giant-Size Avengers #1 Buckler

1967: Fantastic Four Annual #5 Kirby

Giant-Size Avengers #1 (Pt 56) Thor, Vision, Nuklo and Thermal Man

1969: Thor #170 Kirby

1974: Giant-Size Avengers #1 Buckler

Giant-Size Avengers #1 (Pt 44) Captain America, Vision and Nuklo

1974: Giant-Size Avengers 1 Buckler                        1968: Captain America 106 Kirby  

Giant-Size Avengers #1 (Pt 42) Behold The Vision--Flat On His Back

1966: Journey Into Mystery #125 Kirby

1974: Giant-Size Avengers #1  Buckler

Giant-Size Avengers #1 (Pt 4) More Classic Kirby

But wait--there's more to Giant-Size Avengers #1 than just the Fantastic Four. Here are some GSA #1 panels inspired by more Kirby classics from the Silver Age.    
                                                                           

1974: Giant-Size Avengers #1 - Rich Buckler

1967: Tales of Suspense #94 - Jack Kirby

                               

1974: Giant-Size Avengers #1

1968: Captain America #105 - Jack Kirby

1974: Giant-Size Avengers #1

                                                                                               

1964: X-Men #4 - Jack Kirby

                              

1974: Giant-Size Avengers #1 

1966: Thor #134 -  Jack Kirby