CR is the basic version, CRL is the large format version or you could go with a Litecrawler or Nitecrawler if you want one with the works. The universal install kit for the CR series allows you to specify the tube diameter as does the flange selection for the CRL.
The Litecrawler is the go Trevor. I tried their heavy duty Crayford focuser and it did not even handle my QSI683 very well. I needed to use something with a bit more guts. That focuser would meet that expectation.