This page has what appears to be the liner notes from the soundtrack album. There are 2 cuts called IF I HAD WORDS:

If I Had Words. (2:50).
Adapted from Saint-Saens, Symphony No. 3 with lyrics by Jonathon Hodge (Rak Music) derived from original master by Yvonne Keely & Scott Fitzgerald courtesy UA/Liberty.
...
If I Had Words. (1:52).
Performed by James Cromwell. Incorporate Symphony No. 3 (Saint-Saens Arr. Nigel Westlake).

So Westlake seems to be the arranger, not the lyricist. He is also listed as the arranger on several other cuts.

allmusic lists several compilation albums (e.g. "Classic Love Songs of the 70's") that contain the recording by Scott Fitzgerald and Yvonne Keeley which was mentioned in the first message of this thread. I've listened to several overlapping sound samples from various albums and I'm convinced that the "correct" lyrics are:

If I had words to make a day for you,
I'd sing you a morning golden and new.
I would make this day last for all time,
Give you a night deep in moonshine.

However, when Farmer Arthur Hoggett (James Cromwell) sings it, he sings:

I'd give you a morning golden and true.

But heck, he's just a character in a fictional story, right? So he's allowed to make mistakes!