Single or Dual plane?

The dual plane if its an air gap could be an issue for you in cold weather. When I visited Colorado years ago it snowed on September 1st. I don't know what the average winter temp is there but the car my take a long time to warm up with an air gap at the same time leaving a lot of raw fuel to wash the cylinder walls down. Depending on how much you drive the car and if you fully warm it up every time you drive it this may not be much of an issue if you are prepared to change the oil very frequently.