Gee, I'm surprised by that. But Gordon seems to know about this issue.I tried mounting the 101 oil filter to the 105 Block. Turns out this will not bolt up as the bolt centers are way different. Approx. 54mm for the 105 block and maybe 41mm for the 101 Block.
My knowledge base comes from adapting a 1750 block to a 101 Giulia chassis a long time ago (like 25 years), so my memory may be a bit unreliable. I had remembered that a 1600 oil filter housing had just bolted to the 1750 block. And I'd assume that your 105 1300 block was similar to the 1750.
Is it possible that there were different 101 blocks & oil filter designs? Some with the wider, ~54mm spacing? Or is my old memory just faulty? (which would be no surprise)