1979 Corvette Trans or Clutch Problem?

I have a Corvette 1979 with the 350 Horse Power Engine.Question:  My vette has a M21 4-Speed Close-ratio. Drove fine, then in storage for 2 months, and now I can't get it in gear when the engine is running. Goes in gear just fine with engine off. If I try to start with it in gear with clutch depressed the car jumps like the clutch isn't working. Could the clutch plates be frozen to the flywheel?Answer:  Yes sounds like a moisture issue may have seized your clutch disc to the flywheel… best to get it out of the shed and get it out and see if you can get it to break loose.Let us know what part you need we can help you with clutch and or transmission parts.  You can see the M21 transmission parts we can supply on our site.