In 7 years there is a possibility the cylinders rusted if the engine was not sealed and was exposed to mild/high humidity. Maybe a bit of kerosene/diesel in each cylinder for a week or so will free it up..... Also, if it is a stick shift, make sure it is in neutral (with the parking brake on).
If you get it loose, you still do not know the condition of the cylinders.......best bet is to pull the heads and find out exactly what you have. Another possibility is the bearings were installed incorrectly.......will need to pull the pan to check them.
There are a few other possible causes that are a bit more remote, but.......incorrect installation of clutch/TO bearing, incorrect installation of cam, incorrect installation of piston rings......
Good luck......post your results.