Hmm.. I had a shift lite in my '94. Was an Autometer or MSD; it had the yellow rpm pills you stick in it.
It was inaccurate for a 10 cylinder, but consistently so. I think the lite would come on early like at an RPM 20% ahead of the rpm on the pill.
So I just used pills that had a higher RPM that I wanted and the lite would come on just right.
I think it was an MSD lite (it's been 8 years...), they gave me 5
free pills to cover the RPM range I wanted .
I've read where RPM window switches have to be redone at the factory for use on the Viper..is that really necessary, or can't you just set the window switch at a higher RPM to compensate for the 10cylinder 'effect'??