Chaps not to rain on anyone's parade here, but be aware that the 750/101 filter head is shorter than the 105 filter head......in other words the distance from the round flange where it bolts to the block to the centre pin or centre line of the filter screw is different.
The 750/101 filter neck is about an inch shorter as the oil filter can hugs the side of the block to the point where the lower block flange and the oil pan flange have a suitable semi-circular cut out to allow the filter can to clear the block - this is because on the 750/101 the lower chassis rails are virtually parallel to the motor and the steering arms swing really close, so clearance is at a premium.
The 105 filter head neck is about an inch longer placing the oil can away from the block, the lower chassis rail area in a 105 is almost triangular leading away from the motor, so increased clearance, plus the steering bits now work behind the front cross member freeing up space, hence Alfa shifted the oil filter can outboard a bit.
Have a look at Alex's thread here --> 101-105 Spin-on oil filter adapter kit
--> see his first post pictures and look at the neck, then scroll down to post #14
HOWEVER You can still make it work very easily, all you will need to do is machine a very simple suitable circular spacer with 5 holes, (2 for the bolts and 2 for the oil passages and one on the side for your idiot light). This will shift the short neck 750/101 filter head away from the 105 block. This isn't a biggie as Alfa used a +-10mm spacer on the 750/101 Veloce's anyway and they all used the same size filter head. It's the simplest solution - gives you the screw-on filter plus your idiot light and it's fully reversible back to your original filter on the shelf. You will need 2 longer studs, but that's not a biggie as you can loose the fine pitch thread on the outside part and just stick with a coarse thread to save costs
A last ditch Heath-Robinson alternative would be to file the semi-circular cut-out in the lower flanges, but it's irreversible & this is assuming that the shorter screw-on filter would even foul here, but you might even get away with it...... I haven't ever tried on a 105, but I have filed the flanges to fit 105 blocks to 750/101's as you *really* need the clearance here....
The Hurlock filters were the best of the best and Uncle is a straight up guy, the price is what I recall Les charging 10+ years ago, so you are getting a really great deal. I would go the spacer route with a gasket either side and stick my original in a baggie on the shelf and consider the spacer cost as inflation over the last 10 years