Trude Heller, Gloria Toote and Ed Townsend were the three backers of Tru-Glo-Town I believe.
Like you Robb I don't believe there is any connection between TGT and Simpson/Simco other than Jesse Herring working for both, it isn't unusual for writers, arrangers etc to work elsewhere, they go where the money is at the end of the day.
There is a blog article about Trude Heller here https://streetsyoucrossed.blogspot.co.uk/2005/05/trude-trude-trude.html
Article about Gloria Toote here https://www.encyclopedia.com/doc/1G2-3077500058.html