My wish: Someone will give a picture tutorial of how to alter a Mauser floorplate to one with a lever release. That would be an appreciated effort!

I'm doing one now but did not take pictures. I'll try to document what I can of it.

i make a couple batches of them a year.
i machine the latch blank from 1/2" rod and the floorplate bushing from 3/8" rod.
i make the latch blank around .180 long with the 1/2" step .080 thick then drill & tap 8-32.
i started out making the bushing by just drilling a clearance hole for the 8-32 stud on the lever and parting it off to length. then drilling the floorplate hole out to 3/8 and soldering the bushing in but i've started cutting a tapered bushing now and reaming the floorplate hole slightly with a taper ream.
right now i make the levers from 1/4" or 5/16" keystock. i sdtill a hole in one end for a 8-32 stud then weld it in from the top then shape the lever. eventualy i'll machine the lever as one piece.
i use a 4-40 screw through the bottom of the floorplate as a detent and a 6-32 set screw through the side of the latcg blank.
i also like to leave the plunger in the triggergaurd to pop the floorplate off when the lever is turned but i do shorten it a little.

Jim Carmichel wrote a chapter on this in his book Do-It-Yourself Gunsmithing. farktoof's link above has much the same instruction as Carmichel's write-up, plus a bit extra.