I PRESUME you're referring to the front, flat cover for the truck bell housing, correct? I'm not aware of any such template for that cover, BUT, in the below picture, the bottom cover is for a truck housing.
That's the best I can offer.
There were many thousands of the truck housings which eventually have ended up in salvage yards and I would expect that many of them had the cover attached to them. It should not be too difficult to locate a decent used one.
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