Yes, they made that model
Any of the Military grip models will take a magazine with a longer floor plate. For example: http://www.ammoclip.com/H/high_stand_military_grips.htm
1974
1978
Best left to a gunsmith
1958
1941
Best left to a qualified gunsmith
Same as High Standard model 101 .22 caliber pistol. gunclips.net has them for $35 but sometimes the after-market mags need adjustments. I'd head to the local gun show, take your pistol along and check for proper fit. Good luck!
10-1000 USD depending on specifics
25-125 USD or so
1949-1950.