Welcome to SailNet! Attaching the boom to the mast is a good idea. It might help if you could take a picture of the pieces involved and post it here. Without that we have no idea what the setup might be or what part may be missing. Who made the spars? Their catalog might be a place to look.

https://sailboatdata.com/sailboat/mirage-30/

 

Managed to contact rig-rite inc about my old style ISOMAT NB-16 Boom. Have asked them what I need and to provide assembly instruction.

 

Glad to hear you're moving forward! Hope they have the parts you need.

 

My Mirage 24 has a "T-shaped" track (almost a foot long) that rests against the mast. The track is made of plastic with a density between polyethylene and phenolic. The track is soft enough so a set screw on the boom can dig in the track and hold the boom at the desired height. The vertical portion of the letter "T" is about 9/16 inch wide. The top of the "T" is about 7/8 inch wide. The total height of the 'T" is 3/8."
There are counter sunk holes along the track for flat head machine screws. The screws go through a slot in the mast and tighten through cylindrical nuts that are drilled and tapped through the diameter of the nuts.

Sorry I don't understand computer technology well enough to send a pic.
-CH

 

I thnk the Mirage 30 has a heftier setup. His mast is more than 10' longer than yours, with 3' longer boom.