Looks like you're half way there.
Welcome to the forum Andy. Syph007 is a chap who does 58mm SAK modding if you want someone else to build one for you. If you fancy it yourself then I don't know if you've found this guide; https://forum.multitool.org/index.php/topic,43271.0.html
Is there a particular length I need to cut the brass pins, to get a good finish?
For 58mm alox you should cut them very short, as close as your cutters allow. Half a mm above the scales should be plenty.Good luck with the peening
Looking good Andy. I agree, you'll not need much at all to peen. I'll just add that you'll be best cleaning up the cut surface so as it's nice and flat before you start hammering. Might I suggest you go ahead and build it with the bad back scale? It'll be good practice anyway even if you do take it apart again.
Thanks Gareth. Though there’s a bad back scale, and then there’s a “bad” back scale! Was it Meatloaf who sang, “One Out Of Four Ain’t Bad”?!
Hey, that's a good thing! Drill some holes, about 1cm apart in that scale. Then, use it to train your peening. If you miss the pins and hit the scale, there's no problem.
For future reference, no need to drill, you can push the pins through (use a soft underground like wood and a center punch). Warning, only works for Alox 58mm.
It seems to me that your alox Rambler is going to have two front scales...