Ford 4 speed stuck in 4th gear

I have 1966 ford mustang coupe with a 91 302 that has 95000 miles switched to carburated and a boss 302 4 speed toploader with a centerforce dual friction clutch using the 91 flywheel and its non hydraulic set up, with a short syncro hurst shifter with reverse lock out. This setup worked no problem for a while dont know if its meant to work together but driving it the other day I put it into 4th gear at a low speed and now the shifter refuses to let it out of 4th gear I have noticed a fluid leak on the tranny lately but I dont really think that if the fluid was low it would not let it out of 4th and it seems all the linkages are hooked up maybe a bit looser that they should be but connected, the car still grabs when you let off the clutch pedal and it goes into nuetral when you push in the clutch, basically operating the way the way the pedal should, I have no idea cause Ive never come accross this problem ever if you could help that would be great thanks ed