On leaving the Army I worked for a company who packed stuff for the MOD, basically everything from a ball bearing to propellers, turrets etc. I agree entirely with Richard regarding the procedures to preserve engines for storage we used a slave land rover engine on a frame that was connected to engines , gearboxes etc and used to turn them over to lubricate all moving parts. As with everything military, everything was strictly regulated and checked throughout the process and although the shelf life was set at X years we have uncovered engines three times beyond that time that have been absolutely perfect HOWEVER it does all depend on how they have been stored and especially the temperature variations they have been subjected to, the MOD over engineered everything in those days including packaging that's why we are still finding WW2 items still in perfect condition in their original packaging. Unless your engines have been stored in really damp conditions with the original protective wax, plugs etc removed there is a good chance that on doing the usual checks, oil changes etc that you would do with any engine being awoken from a period of storage they will be fine. Money was no object in those days and everything was top quality, so hopefully they will be fully serviceable. Who knows maybe I packed them :-D