Is Wire Size Critical for a Temperature Sending Unit?
 

Last week I mounted a VDO oil temperature gauge in my 914 and earlier today installed the VDO sending unit in the sump. I have some 12 gauge stranded wire which is too large to fit the clip on adapters on each end. If I trim the wire on the ends will this be ok or will the larger wire cause the gauge to read wrong? IOW should I use a smaller diameter wire?

No. It's simply measuring impedance (or is it resistance?) and is very low amperage. The factory wire (0.5mm2) is roughly equivalent to 20AWG.