I had to have my Racing Hart's custom drilled so hopefully I can answer any of your questions. If not, feel free to drop me an e-mail and I will hopefully be able to answer your questions or point you in the right direction!
svt1675@comcast.net I ordered my wheels from a local wheel store. Obviously they cannot stock every wheel, so thy had to order them from the manufacturer, Racing Hart. The manfacuturer will drill them before they ship them, as most wheel shops don't have the machinary necessary to do so. Expect a little bit longer wait from the time you order them to the time you get them since they will need to be drilled. There will probably also be a nominal (I say nominal in comparison to the cost of the wheel) fee for drilling the wheel, I paid about $20 extra per wheel
The blanks thing may or may not matter depending on the wheel. If you look at mine, they have a center cap hiding the lugs. Therefore it doesn't matter if there are extra holes. Mine were re-drilled, but unless I take off my center caps, no one will ever know outside of this post.
If the wheel has exposed lugs, then obvioulsy they cannot re-drill them and will have to use a blank, or a wheel w/ot any existing holes.
Ask whoever you are buying the wheels from to see if they are available in a 4x108. If they say no, then inquire about getting them drilled. They may require a deposit so they are not stuck with an odd bolt pattern wheel. Ask them, again depending on the wheel, if they will be drilled from blanks or re-drilled to match.
I spoke with Axis before deciding on my Racing Hart's and they can custom drill to any pattern, within reason. Antonio probably had to have his Axis's custom drilled also. Obviously any wheel that tirerack or tires.com lists will be pre-drilled to a 4x108, so the only time you have to worry is you are shopping "Outside the box" so to speak.
This is a pretty common thing, or so I would think, and the shop I was dealing with and Racing Hart had no problems filling my request. For example, call Axis direct in California, ask them if there are any authorized dealers in your area they can point you too. If not, start asking them about the bolt pattern and the possibility of custom drilling to a 4x108.
I hope that answered all of your questions, if not, like I said drop me an e-mail and I'll do what I can to get you hooked up.