Any particular reason you want to keep/modify the 58? Because if not, I agree with those above; sell what you have and buy what you need/want.

Since ammo cost seems to be you're main incentive, of your options, 45 auto has the advantage.

FORGET THIS, was thinking Mod 28: Also based on cost, think about a 9mm cyl conversion, with or w/o full moon clips.

Or use the money you were going to use to convert it/buy something else, to buy reloading equipment.

You can also load .41 Special for more enjoyable shooting fun!

__________________
Jim
S&WCA #819