I’d probably grab my Fein multitool with an offset blade.

Les 

I recently installed one on my 1990 C36 STD Rig and did not have to lengthen the gate. I took the boom off at the goose neck and it slid right up.
Tim

Mark.
I installed a Tides Sail Track on my 1990 Hull #1041 and did it very much the way Tim did it above. My total gate clerance is 3.5 inches and I did not find that any cutting or additional clearance was necessary. If you are not going to remove the boom, be sure the corners of the gate are smooth and well very lubricated. See; https://www.youtube.com/watch?v=Yta5TOVvDIA  for a few tips and hints on how to do this.
Bill

I installed one on my 1990 and did not have to do any cutting

Mark:  Like the rest above I installed mine without modifying the mast gate.  I did smooth the edges like mentioned above too and it all slid up very nicely.  Having some sun to warm the track up and an extra hand to help control the roll of track helped as well.  The one thing I did (after several years of fighting it) was to replace the toggle that was included with mine to hold the bottom in place with a drilled and tapped bolt into the mast track.  The problem was that the Tides track would slide down and rest on the sail tack.  I would have to push the track up and hold it while loading/unloading all the cars each spring and fall. So far so good with that modification.

I installed mine a couple of weeks ago.  I could not get the track to fit without lengthening the gate.  Maybe I didn't try hard enough.  I do not have a grinder, so I used a metal cutting wheel in my skilsaw to make the initial cuts and then cleaned it up with a dremel.  It worked great and I had no real issues.  Even then, I still had to lube the track with soapy water to get it all the way up the mast.