Well, if both engines are 4.0s, you didn't say, they will swap in the same. I would not drop the extra cash on the motor just to save on 15k miles. While you're at it you should go ahead and build a stroker engine. I mean if you're pullin the block any ways all you really need are the crank and rods from an old 4.2 and then later if you want to upgrade to larger pistons cams ported head and all that you already have an extra block to work with.
[B]1999 4.0 WJ Limited [/B] NX Wet EFI Kit;HESCO Head, Cam and Water Pump;Apexi SAFC2;Accel 24lb injectors;K&N FIPK; 2.5" Dynomax Ultraflow SS Exhaust; Dynatech Cat; Banks SS header;Custom 3" Head Pipe;E Cut-out;62mm TB & Spacer; MSD DIS-4; Jet 180°stat;H&R springs;Eibach Sway Bars;Brembo Rotors; Streetscene grill;E.L. Dash ; Autometer C2 EGT, N2O & Fuel Pressure;Edlebrock A:F Meter