Mile High..
 

What would the difference in times from sea level to 1 mile above in the 1/4mile be? (Ex 1/2 second etc.)

Really depends on DA.. on an NA car it can be somewhere around .7ish up to a full second I think. I have two tracks somewhat near me, there's almost always about 1000' difference in DA between them. And I consistently get 2-3 mph higher and better times with just the 1000' better DA.

Depends on a lot of things for instance how much power you're making. Here in Abq the 8,000 DA sucks

Another way to look at it per 1k feet a na motor will lose about 3% in power, so at 8k your car has lost an est 24% or on 426 flywheel about 102 hp, so based on that you have lost about a second on your 1/4 time