changed the engine and do not start

Hmmm...Hal, my opinion would be to revert as much as possible back to the original set up, including swapping the 1999 electronics onto the 1997 engine. This way you may move some sensors and components, but not the ECU and the harness, which would also possibly change transmission operating strategy as well as anything else that thing gets into. You could probably go either way, just as long as all components are agreeable. The 1997 and 1999 model are identical vehicles in many ways, but Ford does show a different part number for the engines.