Have my 79 IT400F crank rebuilt and ready to install. New main bearings installed in cases. I have a Tusk crank puller which will pull the ignition side of the crank into the case with supplied attachments. The clutch side is another story. Tusk pull comes with 8mm and 10mm threaded adaptors to fit the end of the crank. The clutch side thread on the crank looks to be 17mm. Anyone know of a puller that will fit on this side? Or do I need to freeze the crank, heat the bearing on that side case and drop the crank in and then use the puller on the ignition side to pull the cases together?

Clutch side normally is a "slip fit" in my experience.  No tools needed.

Yep sliding fit right side or just hand wipe some fine wet n dry paper around the shaft & oil then is a fitting slide push in.