engine placement?

[Greasey Harley]

Is there a guide to engine placement?
I have 2 '68 Chevy trucks.
Both factory 327 trucks, both factory 4 speed trucks.
The C10 swb has the motor in the forward position.
The K20 4x4 has the motor in the rear position.
I am fairly confident that both trucks a re original, as I know the history of both.
Is there a guide to engine placement?
I have searched a little bit, bot haven't found a definitive guide.
No issues with either setup, just curious.
-Russ