Do not alter the OEM springs! I have 'repaired' three such gunsmith 'trigger jobs'. The flat hammer spring is too easily bent out of plane of it's intended bend - and clipping the end of the trigger return coil gets the flat surface off - and leaves a burr that can also drag inside the trigger block. New lower rate springs are inexpensive - and you'll have the OEMs to return to, should you be so inclined. As to spring rate choice, if you are a competitor, time is more important than the softest trigger. You need a quick return on the trigger - retain the original return spring or use the stoutest example from the Wolff kit. For reliable ignition with a 625, ie, moonclipped .45 ACPs, consider the 'full strength' hammer leaf - it will still be an improvement. Only go to the reduced level spring if you can limit your ammo to Federally primed.
Now - the real key to a 'proper' hammer leaf replacement - the strain screw. In the 625JM and 627 Pro, at least, the 'tuned action/trigger' means a filed strain screw to 'fit' the flat spring. It will work into the hollow back of the ribbed Wolff spring, lessening it's pre-load - but making for a light trigger. Sadly, it also makes for ftfs. Get thee to a Home Depot - Fastener aisle - look for the cabinet with drawers and odd bits. You need a hardened SS 8-32 x .5" socket headed set screw. If you don't have an Allen wrench to fit, you'll need that, too. The set screws are poly bagged 2/$.56. Some blue Loctite is needed, too.
The gun must be unloaded. You should have the new spring in place - the sideplate on. Coat the set screw's middle with blue Loctite - allow it to slightly set - 15 minutes. Insert it, and, if it's a rimfire, put some snap caps in the cylinder's chambers. After getting much of the new screw into the frame, test the DA trigger - adjust it to get it about where the trigger feels like it did with the ftfs - give it a 1/4 turn CW (in) and test the revolver with live ammo - at the range. If you still have ftfs, another 1/4-1/2 turn CW (in) should take care of them. When the right spot is found, set it aside overnite to permit the Loctite to dry.
Another approach some use is the 'extended firing pin' - which isn't extended, it just has a bit more range due to a wider slot in it's barrel. It can flatten the miniscule fp return spring, so I don't use it. If your fp is really short or worn, get a proper fp. With moonclipped .45 ACPs, flat moonclips, a clean area under the ejector star, Federal primers, good brass (I buy fresh Starline - for my revolvers only - $137/1,000 delivered - no range sweepings!), etc, are all important. Ranch Products had their excellent moonclips blued for ~$30/100 delivered.
A smooth trigger with MIM parts is easy - clean the manufacturing dirt/crud out of the frame innards, lube & re-assemble. Dry fire 1,000+ times. Repeat clean and very lightly lube - voila, instant 'trigger job' (And a stronger trigger finger.).
Remember - competition means speed - fast trigger returns are important, so that spring should be stout. For us mere mortals, soft springs - and Federal primers - rule. Save the OEM springs!
Stainz
