Engine downsize 280GE ----to 230GE ??

Hello Søren,

It is possible to do what you ask.  But there will be a few modifications that will needed to be considered.

The 280GE engine has its starter on the Right Hand Side (Viewing from the rear of the vehicle, looking forwards), the 230GE engine has the starter on the Left Hand Side, so to fit the 230 engine straight to the 280 gearbox is not straight forward.  You can change the bell housing to accommodate this difference, with that, you will need a 230 engine's starter motor.

Alternatively, when you choose your 230 engine, consider transferring the gearbox off that same donor vehicle, this will over come matching issues. 

You will need to consider the shape of the sump to make sure this will not foul with the differential housing.  Here you will be looking to source a sump and perhaps a suitable oil pump or oil pump pick up.
Not having done such modifications first hand, my suggestions are only academic; therefore, I can not positively say if the engine mounts will fit the chassis frame or if you will need to adapt its fitting, like wise the same for gearbox mounting, should you consider a gear box transfer as well.

Before going ahead with any modifications please note  any engine numbers' and, or gearbox numbers' so that a comparison can be made to see if it possible to do the prospective changes on paper, as it were.

Obviously, you will then have to make visual comparisons etc, etc...