3 speed auto

abc

If the tranny shifter does not have a button on the drivers side of the shift lever where ur thumb woud go, it may be a 3 speed.However most Mazda automatics have overdrive.RU sure your 4 wheel drive hubs arent engaged?That would explain the low top end.u can swap it out with a 5 speed but since the auto tranny case is much longer than the manual one u will need to get the 5 speed drive shaft as well,plus u will need to get a different u joint for the rear.Also the 87 engine is a Mitsubishi,so I am not sure about the bolt up from engine to tranny.BJ