grinding first and reverse

I need help with my tranny. I grind in first and reverse unless I make a smooth transition from 2nd to first. 2nd and 3rd don't really grind at all. It's a 3-speed manual with a 200 c.i. engine. If I'm in neutral, it doesn't matter how long I hold the clutch down, it still doesn't slow down enough for me to go to first or reverse. I even tried turning down the idle mixture on the carb but it still grinds. I have changed the gear lube also. I think I need a new clutch because the clutch pedal won't return to it's original starting point unless I put my foot underneath it and pull it back up. The only problem is I can't find clutch parts for a 65 Mustang with a 3-speed. Any ideas?

I think your on the right track I would start with the clutch. Have you tried adjusting it first?

try NAPA for a new clutch... if they don't stock they should be able to order it. the other auto stores like advance and autozone aren't likely to carry older stuff.

I appreciate those who replied and tried to help me. My father-in-law came up with a bright idea to spray WD-40 just past the clutch fork and boot. Well what do you know? The old man aint so dumb after all. I did it and it worked. I also sprayed just a bit on all the linkages and up around where the shifter is. Everything is as smooth as can be. Although, it's still 36 years old so it takes about half a second before you can put it in first or it growls just a tiny bit, but I'm sassyfied. I've tried everything including adjusting the clutch. But the old WD-40 (which I swore I would never use on a car) actually did it. You should also know that the boot on the clutch fork was ripped so that WD-40 may have knocked off any dirt or dust that was holding back the pressure plate or springs or something. Thanks again