When I purchased the car, it was possible to buy a second spare engine.
The engine which belongs to the car consists of a XK120 block and XK140 head.
The spare engine consists of  a XK140 block and XK120 head.

To be able to build a complete XK140 engine I decided to buy the extra engine for Euro 750.

Engine 1:

• Head G8877-7
• Block W1800-8

Engine 2:

• Head W7707-8
• Block G9274-8S

Now after almost 5 year I started to disassemble both engines and found, due to 46 year of stagnation,  the following issues:

• Sparkplug snapped of
• Thread for sparkplug gone
• Combustion-chambers damaged due to corrosion
• Cylinder wear 
• Pistons stuck in cilinder
• Inlet and exhaust valves/seats damaged due to corrosion
• Wrong type of camshafts mounted in the XK140 head (C13080 and C2444, required c5717 and c5718)

Hopefully it will be possible to combine the good parts from both engines and try to find the missing parts.