Range Rover & Discovery Engines - Interchangeable?

[rockcity]

Is the P38 4.0L interchangeable with the Discovery 4.0L? If not, what's different? I've been looking for an engine for my 97 P38 and I find that if I search for the Disco engine, there are more available and they are far less expensive. Any insight would be helpful.

 

[joey]

Same engine if 4.0...