What to look for when buying an engine.

Got a throttle body adapter plate from EFI source to fit a LS throttle body, but the ID of it is a bit larger than the ID of the flange on my intake. Is the ID on the car intakes larger than on the trucks?DSC_0465.JPG
I could try to "port" the intke for a smooth transition or would I be better of by making a new adapter? Haven't sourced the throttle body yet so not sure which size I will go for...