do this for me:
start on FLAT, open land with the car in nuetral and no p/brake start the carshift into 4th gear and try to go like you would in 1st
if the engine revs: buy a new clutch kit
if the engine stalls/dies check your hydrolic clutch lines for crimps, binds etc.since the car sat the dot3 couldve absorbed water/debris.icr if you did or not but try to bleed new dot3 into your clutch system.
BEFORE you replace the transmission itself go to advanced and pick up the Lucas Manual transmission oil. drain old oil, fill with lucus.
hope this helps; please keep me updated