I'm in the same boat, motorcycle's cars (mostly old Alfa's and BMW's) As you say, there must be a club somewhere that would value these items, but one thing to remember is that with the introduction of unleaded fuel....All classic cars and bike's have to have the valve seats and valves hardened. The additives just don't work, and as a result, the sad fact is that many clubs have gone into decline.
I did my last re-build in 1998 ( A Honda 550 Four) and an Alfa Romeo sud (rescued from Italy)
I have not attempted one since, and of course health would not allow it anyway..All I can suggest is that you have a browse through some of the classic car sites and mags.
I binned a few hundred old car brochures a couple of years ago. Sent them to the recycler. '70s/'80s. They were just clutter to me, the remains of a collecting hobby I used to indulge in during my long lost youth. Looking at them, I realised that I just didn't care any more.
Should I have made an effort to sell them? No, because I never sell anything privately. Money isn't everything. Should I have made an effort to pass them on to a collector for free? Again no, because I couldn't be bothered.