I don't have one to swap, keeping mine! However a lot will depend on size. Most on the surplus market are smaller sizes and they are fitted, kinda like an of the shelf 'Tailor made suit'. So small in the waist with a classic V-shape cut, so very dependent on your on shape, you'll need a smaller waist then chest by a decent margin! I do have a Swandri ranger (In the blue, funny enough, are they small cut? Mine was second hand and its not generous), in size large thats fits perfect and my Swedish Tunic (and Greatcoat, but thats another story. Awesome coat. Oh and my leather officers coat, oh my. As you can tell rather partial to Swedish kit!) are both size 96. Normally I am a medium to large dependent on cut, generally a more classic man shape, by which I mean small waisted, V shaped (so my wife says)...
Oh and yes they are well worth it. The rear pockets are very good. I have carried, a BCB mess kit ( with an Alcohol stove and brew kit inside) on one side and an old German army Aluminum water bottle (Filled with boiled water before leaving, hmm toasty kidney warmer) in the other on a winter bimble with just a thin wool jumper and a wool shirt under at 0c and been very warm. No backpack and a brew-kit is so nice.
I hope this will help with getting the fit correct.