Brushless advice

[tracksntreadslou]

I recently purchased a new leimbach pump and this pump does not have a motor yet ..I want to install a brushless motor ..I was looking at the upgrade for them at leimbachs website and with so many available from tower I thought I may save a few bucks by buying here in north america..Tower has a very wide selection
Question is which one is comparable ?
This is the specs leimbach has for their brushless ..I am not quite sure what the shaft size is


•Operating voltage: 12V or 7, 2V
•Speed: 0 to approx. 12000 RPM
•Receiver power supply: 5V Max 3A