This car is actually 1986 300 SDL

A blown head gasket may allow coolant to leak into the cylinders and hydraulic lock the cylinder. If enough coolant enters the cylinder on the compression stroke the valves are closed and the piston travels upward trying to compress the coolant which is a solid, it becomes unable to compress a "solid" and prevents the engine from starting. A badly blown head gasket in which case the cylinder no longer contributes or makes power will make the engine difficult to start as a diesel engine needs good compression to build heat to produce combustion and run.

Common! it's clear someone told you you had a blown headgasket. NO YOU CANNOT DRIVE THE CAR!!!! Unless of course you are up to buying a new engine. That is more than the car is worth! If you are going to let it sit that long you'll have to put an additive in the tank. Diesel fuel goes bad alot quicker than gas.

I agree-Don't drive the car in this condition. It will only cause catastrophic engine failure!