JT, you mention a 7.5" barrel, which makes me think you're looking at an SA type, probably a Ruger Blackhawk/Vaquero because most of the Italian SAA clones can't handle .44Mag.
If so, having studied the matter, I'd buy a .45LC version for the following reasons:
1) Low-power plinking/practice loads are widely available in a full-length shell. In .44Mag, your low-power practice ammo is .44Spl, which is a shorter case and could slightly affect accuracy.
2) There are also high-powered .45LC+P loads that rival the .44Mag for raw energy and effectiveness, at slightly lower peak pressures because of the increased case volume. See also the hunting ammo at
http://www.cor-bon.com for examples. In their self-defense ammo line, their .45LC defense load is very similar in power to their .45ACP load, which is fine.
3) Ruger's twist rate in .45LC SAs is 16:1, which is optimal for self-defense class loads (200grains at 1,000fps or similar). Same twist rate the top 1911 makers use in their .45ACP slideguns. And it's not a bad twist rate for hotter stuff, although at some point a slower twist (20:1 or so) for the really fast loads would help.
4) You can have a gunsmith fit up a .45ACP cylinder to any Ruger .45LC SA gun, Blackhawk/Vaquero/Bisley/whatever. That would really open up your ammo options, and allow you to use cheap GI 1911 7rd mags that are $5 a pop at any gun show as speedloaders
. Proper bore for .45ACP is identical to what Ruger does on their .45LCs, which is also the most common post-WW2 bore size for .45LC and what all the .45LC ammo is set up for. So I wouldn't sweat the fact that there've been two different .45LC bores (modern .451 versus old .454).
Hope this helps. I'd buy a .45LC and do most of my shooting with lighter-power rounds for defense (equal in power to .45ACP) or plink with even milder "cowboy loads", and reserve the hot .45LC+P for woods/hunting carry.