Can you not just use a used SW20 3sgte crank pulley? gen2 or 3.
 
When I built a tough gen2 motor many years ago I used a 5sfe crank in a 3sgte block using the original gen 2 3S pulley. I used the alternator in the factory location along with A/C compressor. No issues at all and is still pumping out 320KW ATW today after apparently 40+ thousand KMs.

Sure an aftermarket damper isn't cheap but it will help your engine live a long and healthy life! I'm using a Ross on my build and talking with my tuner he recommends a damper on all his builds whether its Ross, Ati or Fluidampr etc.
 
In his experience the engines with them lasted longer then those without. Why not spend a few hundred extra now when you've gone to the trouble of building a 5sgte?

I just used a OEM 3s one on mine

Aftermarket crankshaft pulleys are not a good idea.  Have had several engines over the years that cracked cranks due to harmonics destroying them.
 
Just use a stock one and leave it at that. :)