Holley's jetting instructions for a 4150 Ultra HP Series:
Carburetors are calibrated at 70° at sea level. Decrease the jet size one number (approx. .002) for approximately every
2000 ft. increase in altitude. Increase jet size one number for every 35° drop in temperature.
Here's a converter:
http://bgsoflex.com/auto.html
They also have numerous other calculators