To begin, the motor mounts will be different and for that reason alone, no, it will not fit exactly.
Cadillac never made a 400 engine
That depends a lot on the amount of maintenace and regularity of oil changes the engine gets
The 2007 Cadillac Escalade has a V8 engine.
The 2009 Cadillac Escalade has a V8 engine.
The 2003 Cadillac Escalade has a V8 engine.
The 2006 Cadillac Escalade has a V8 engine.
The 2012 Cadillac CTS has a V6 engine.
The 2009 Cadillac CTS has a V6 engine.
The 2012 Cadillac SRX has a V6 engine.
The 2012 Cadillac Escalade has a V8 engine.
The 2013 Cadillac CTS has a V6 engine.
The 2006 Cadillac CTS has a V6 engine.