Sound upgrade for older GG1

[NSthoroughbred]

I have 3 older Williams GG1' s with "horn" only and would like to upgrad these to correct GG1 horn.  Any suggestions?  Will the new Bachmann Williams GG1 sound be able to be added?

[trainyardjp]

JP, of Acton MA, USA writes:
I would imagine that you could find sound kits, from '3rd party' companies, such as QS Industries: http://qsindustries.com/, or Electric Railroad Co.: http://www.electricrr.com/, or Dallee Electronics: https://www.dallee.com/.

Hope this helps.
-JP