The short answer is no, you cannot swap either of the VR6 engines that came in later models into your 1996, which has an inline 5-cylinder. With enough money and parts, just about anything is theoretically possible, but the modifications required to do this come very close to replacing the entire cab and forward chassis with parts from a later model Eurovan. Enjoy the relative simplicity of the inline 5. The best way to increase performance is to reduce vehicle weight.
2000 HR Endeavor 40PBD
Freghtliner XC, CAT 3126B
2000 Holiday Rambler Endeavor 40PBD
Freightliner XC, CAT 3126B