1988 is right on the cusp of the DDEC intro. IIRC, CA engines had it, but the other 49 didn't. Clifford or Don will know.
There are so many buses out there right now, better to buy one with the engine/transmission you want in it up front than go thru the madness of converting it to something it wasn't when it left the factory (DDEC back to MUI).
BTW, that 8V92TA is a good engine, as long as you keep it cool. Doesn't like getting overheated at all.
Also, if that Prevost is a wide-body (102), there will be more room inside than a similar vintage MC-9. (Technically, MC-9 production ended about 1985 w/ the intro of the "A" series, but there were a few built after that. The MC-12s are virtually identical to a 9 - all were built for 'Hound, run hard and put away VERY wet.)
FWIW & HTH. . .