Using the sources mentioned below, I think the turnpike mostly followed the route of the modern A417, although how it joined it from Ledbury I am not sure - possibly at The Trumpet junction with the A438.
I have found a notice in the London Gazette archives giving notice of an application to amend the act of parliament relating to this turnpike. The page can be found here.
The National Archives, at the Herefordshire Record office, holds a bundle of documentation relating to this turnpike. A list can be found here.
An abstract of accounts of the turnpike trust can be found in some Parliamentary Papers available as a free ebook download from Google Books, here.
The papers of the Biddulph Family of Ledbury include information and a plan of the Ledbury turnpike roads. The catalogue of these papers can be found here. These papers are held by the Herefordshire Record Office and therefore are probably available for public access.