The clutch and pressure plate seem to be stuck on my '68 327 Chevelle 4-speed as it jumps when I attempt to start it in gear with clutch pedal pushed in. I can start it in neutral but it will not go into any of the gears. Car does sit a lot but was driven a little over a month ago. I have tried starting it in gear but so far no luck. Any suggestions on how to get it unstuck? Thanks in advance for any suggestions you might offer.