3.5 V-8 a downsized 6.3?

[berfinroy]

The similarities in appearance between the small V-8s of the late 60s (and into the 70s and 80s) stongly suggests that they are really just downsized versions of the original early 60s big V-8, the 6.3 that later became the 6.9. I mean, why reinvent the wheel?
Would those of you that are intimately familiar with the design of both care to comment?

[Frank Reiner]

The relationship of the two is:
Both are V8s
Both have single overhead camshafts & two valves per cylinder
Both made by Mother Benz

Otherwise they are two different designs, not linked by scale.

[Campbelljj]

Ditto. Related yes all from mothership. Distinct motors otherwise

[Tomguy]

The 3.5 and 4.5 were the same "Family" of engines and directly linked. The m100 (6.3 and 6.9) were unique completely.
From M-100 Message Board - The rebuild starts !,
An m100 block:


From Tony H, and his 5.6 iron block build, a 4.5 m117 block:


Completely different!