Info online indicates John Diehl Jacksonville was originally filed by an out of State entity and there was a Fred Diehl Chevrolet in PA so good chance they may be connected?
If any help, here's links below to an 2011 eBay sale '69 Camaro 307 car w/ John Diehl POP & paperwork also a thread w/ an old Service Mgr. from Fred Diehl who's a '67 Camaro owner...
http://media.collectorcarpricetracke...0476247138.pdf
http://www.theprogressnews.com/default.asp?read=28952
Good luck!
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete