Sorry, biology major in college. Perhaps you could explain the
(commonly used) grammatical difference?

Shawn,
Even though I qualify for English as a second language, I'll give
this a try. For the initial phrase "God Is My Tow-Pilot", the subject
of the sentence is God. The words "my tow-pilot" are descriptors of
God. While this is a twist to the book "God Is My Co-Pilot", the focus
in this wording is God as a proper noun. God is.
In the reversed wording, the subject and focus is on Tow-Pilot. A
human being. Not just any tow-pilot but my tow-pilot. My Tow-Pilot Is.
God is a descriptor in this case, and without asking the author of
this particular statement it is not possible to determine whether the
capitalization of God is due to title case or if the speaker is using
the proper noun God. If the capitalization is due to title case, there
is an implied 'A'. My Tow-Pilot Is A God. Either way, it is a stretch
that a human being could be considered a diety.
The reader is left to some interpretation of what the sentence,
as presented on the shirt, means to them. For me the presented wording
on the shirt is a good reminder that God makes all our blessings
possible. We can't even start without God.

Horst
L33