The ECM 3854369 is a VP number and is used on 5.7GIPHUS, GIPMDA, GIMDACE and GIIMDA acording to OBD Diagnostics. Another clue its VP are the multiple breakers
Being for a VP, the ECM would not use a shift interrupter. Should be doable but
Merc never used a MEFI-1 with EST ignition on a V8...