John,
I would suggest .32-20 instead of .25-20, and don't see any point to a form die set for the .32-44 as all it can possibly be doing is expanding the cartridge, and starting with .32-20 this is already done. Recent Remington .32-20 which I have measures .345 at the base, the same as Suydam lists for the .32-44. You could also use .32 H&R Magnum brass trimmed to length. It will bulge a bit, but after the first firing it will fit just fine. You may have a few cases split, but probably not.
All it should take is thinning the rim slightly, if your gun requires it, and trimming to .980". Run the case into your expander die and you are done, and saved $150! I would ask, are these really "Form" dies, or a loading die set with an expander to open up .25-20? I would go to CH-4D for loading dies, they will probably be 1/2 this price.
This cartridge is a "true .32", unlike most cartridges called .32. Bullet diameter is closer to .320-321 for which you probably will need to have a custom mould cut. I would suggest a bullet like the RCBS .32-098-WC, only cut to cast .321-323.
.32 S&W Long or .32 Long Colt loading data for the same weight bullet using starting charges should be very close. A case , full to bullet base, of Trail Boss will work too. Of course you could use Black Powder too. Fill the case about 1/16" higher than where the bullet base comes to so the charge is slightly compressed, use FFFg. This is a very mild cartridge even for a top-break. There shouldn't be any worry about straining the latch unless you try to hot-rod it.
If you want to slug the bore of your revolver and mail me the slugs I would be happy to measure them for you. I do have the correct guage block to measure a slug from a 5-groove barrel.