Question on calculating RPM at given speed x gear

[99SVTAddict]

Is there a calculation that would tell you what RPM you are at given this:

Viper T56
4.30 rear gear
27" tall tire
122.4 MPH.

I would like to know what RPM I was at when crossing the traps in 4th gear.
I know there's a calculator out there but can't remember where and I don't know if it takes into account the tires size (if that even matters).

Thanks.
Chuck