Rob van meel in the netherlands has really good re-print 17 pdr parts manuals for sale.I bought one a few years ago and it is very useful.
www.robvanmeel.nl
As for your project it seems we are both in the same boat so to speak my second 17 pdr had also stood on a range for many years being shot at and what with the weather playing its parts for 50 years its not a pretty sight !
Rob................rnixartillery