I forget who wanted these measurements, but here they are:

Bare Block:
-front to back: 17 & 1/8 in.
-across: (head to head) 21in
-across: (bell housing)- 16 & 3/4 in.

block with timing chain cover:
-front to back: 21in
-across: (timing chain) 23in
-top to bottom: (timing chain) 24in