Ok, this should be the final look of the Guide Assembly. This is my version and its not very precise according the fasteners used, but I think its enough to get the overall picture.Maybe some explanations for the fasteners is needed.
My version will use: bolt DIN912 M10x55, fully threaded; the washer under the head is DIN125, for longholes DIN9021 should be used, but you won't be able to use the "side-ways" aligning feature; the sheet metal counter nut from above is DIN7967 M10; the clamping nut below is DIN6330 (1,5xd) M10 - it has one spherical end, which should match against 120deg chamfered DIN125 M12 washer (except with a 120 deg "zenker", you can do this with a suitable diameter, properly sharpened drill ). As I mentioned earlier this clamping is not recommended, because you will have to counter hold the DIN6330 nut if you want, let's say, to align "side-ways".
The proper, but way more expensive way of fastening should be using a modified and glued (to the middle flat-bar) stud, spherical washers DIN6319 and DIN985 or similar self-locking nuts.
The 4 stopper bolts from above are DIN914 M6x12 (conical ends) - maybe longer would be better .