Before tearing into it you might want to try some stuff from BG called syncro I think. Maybe someone can chime in with the correct name.
Anyway, I had the same problem, changed out the hyd clutch cyl and it still did it. Not to say that's your problem, but for me it wasn't. The BG syncro oil worked wonders. Since then I had to work on my tranny and the shop dumped the oil. I have to getr more because just trying to get it in 1st is hard and 3rd grinds.

1987 Dodge Raider rebuilt Quest block bored .040 over put together, and installed by Shelby. 5spd, '87 stock turbo, Intercooled, 2.5" exhaust. MPI with hard pipes, FIP Pro-4, MSextra MS1