Hatz 2G40 Remote Oil Filter

[tappy]

I'm using a Hatz 2G40 engine and wish to use a remote oil filter to improve the fit of the engine into the frame. Such a set-up might also allow me to use oil-filters more readily available than the Hatz ones too.
My questions are:
1) What filters can I use instead & how / why are they interchangeable
2) Where should a remote filter be placed relative to the existing one to avoid oil circulation or air-lock problems
3) What other things do I need to be careful of / pay attention to when designing the remote system

Note also that the engine appears almost identical to Ruggerini / Lombardini 950 air-cooled twins, with the only significant differences being the cylinder head layout.