I found a 2003 Cadillac deville e fan that's 30in W and 15in T. So if I put it on my truck it will will cover size to size but top to bottom will be short by 4in. Would that be ok and still fully cool the motor

 

Need to try and find the cfm rating for it. It doesn't matter if you have one fan or ten, if there aren't enough cfm's, it wont keep the motor cool.

 

it should do fine. maybe better than fine.

just be sure and do your wiring right with adequate wire size, fuse, controller - with on/off based on temp control and AC on/off.

are you going to ditch the shroud, or mount the fan inside the shroud.

any idea how many amps it draws?

 

If it can keep a Cadillac deville cool with a one core rad I think my truck will be ok. And shroud is being pulled

 

you also have to remember you are comparing a car to a truck. cars are more arrow dynamic than a truck so they require less to keep them cool. knowing the cfm rating and power consumption is important unless you can get them cheap enough that it is not much of a loss they don't pull enough air.