Here are the measurements
I don't own a Ranger 26, but have one in my boatyard. The boom is now beside me.I didn't bring a camera today, but will try to remember tomorrow.The boom tube is 10'6" over all (not including the gooseneck)It is an oval shape - about 2.25" x 3.5". If you went to Dwyer Mast Co. the closest section they have would be their DM-375 section. It is 2.25" x 3.75" and the same oval shape. It would work just fine.The boom that I am looking at was obviously rigged for racing. It has an internal wire outhaul (with MA) and also an internal flattening reef outhaul. The reefing hardware is on a 1/8" x 1" x 3' track (starboard side). There are two cheek blocks on cars which move along the track to accommodate the obvious two reef points. You don't need a track, but can attach two cheek blocks to the boom inself, but the positioning is determined by the location of the grommets in the mainsail. If you only have one reef point in your main, then one block is used instead of two and if you have no reef points, don't install anything.If you have a flattening reef in your sail, then you can go fancy like this boom or us a cheek block, eye strap, line and cleat in a manner similar to a regular jiffy reef. It will be external and you lead the line forward to a cleat nearer the mast, but still on the boom.The attachment for the boom vang is 42" aft from the gooseneck.The center of the aft black line (outhaul end) is 8.5".At the end of the boom where the mainsheet attaches (end boom sheeting) there is a tang which rotates on a bolt in the outhaul casting end. The mainsheet attaches to this tang. This boom does not have it, but you can add a 2nd tang to rotate up (instead of down like the mainsheet one) to attach a boom topping lift, if desired.The gooseneck end has a casting with a 2" SS post that will attach to the gooseneck attachment on your mast. If you don't have the boom hardware to retrofit to a new boom, then you might have to change the whole gooseneck system to accommodate what parts are available to you now.I hope this helps. I will take some photos and get them either out here or give me an email address and I will email them directly to you.Good luck. Let me know if you have any other questions.