Bill, I have a 1905 HE that I inherited a few years ago. I have gone through what you are going through right now. You search all the forums on the internet and find several conflicting answers as to what ammo to use. I even emailed S&W (no reply). After a few weeks of research, here is what I found for what it is worth (note: most of these answers have already been given here)
1. Yes, there was a 32-20 high velocity round that was manufactured for rifles only. As stated earlier, it hasn't been in production since the late 60's. Some of it is around still but it will say "For rifles only" on the box and has HV stamped on the end of the brass
2. Cowboy rounds are safe to use as they are light loads to lessen recoil and make trick shooting easier. They are expensive and usually out of stock. See Black Hills Ammunition
3. These cartridges are not the easiest to hand load as the case is very thin and the brass can be hard to find in stock.
4. The 32-20 round is rifle ammo. The pistols were made so a guy could carry a pistol and a rifle and only one kind of ammunition. I have not found any production 32-20 (beside cowboy rounds) that are labeled "for pistols".
5. I use Remington 32-20 express rifle rounds #R32201. It is a 100 grain lead bullet. muzzle velocity of 1210 ftps and energy of 325 ft/lbs (from a rifle). It shoots great. I would stay away from any jacketed ammmo if you find it. Watch for leading in the barrel. I haven't had any problems with that but I have heard of others having that problem.
6. The above ammo is still hard to find and runs about $40 for a box of 50. Try Cabelas and remember to look under rifle ammo and not pistol ammo. Pretty expensive for plinking but what do you do?
7. With a gun of this age, you probably want to have a competent gunsmith take a look at it. You just don't know what has been done to it over such a long time. You want to make sure there is no cracking on the cylinder and frame or bulging of the barrell. A lot of these have shot the HV ammo by accident
8. These guns are fun to shoot!
9. Someone is liable to say I am full of it. ( usually they would be right)
Here is my HE ser #32xxx
I hope this helps,
Eric