850-900 ft elevation sounds about right.

There are a few, but this one has track's listed for elevation and "estimated" conditions for any day. After using their estimate, you can change the numbers to actual track and hit calculate again. The big thing is putting in the correct barometer, some calculators want "aviation" barometer and they correct to track elevation. Others want actual track barometer (most), or you can put in zero track elevation and actual track barometer.

Drag Times calculator

Also:
http://wahiduddin.net/calc/calc_da_rh.htm

And the tons of them at Wallace Raceing:
http://www.wallaceracing.com/adi.php