I highly recommend part number 6465K7 from this page:
http://www.mcmaster.com/#gas-shocks/=oru47qAfter installing a fresh 6465K7 shock on my door I couldn't pull it down. I used a small allen key to let a little gas out at a time until I could pull it down and the door would go up on it's own.
This shock takes all the guess work out and it also has a cushion at the top of it travel. The shocks from naerc didn't have this cushion. The door would go up and slam hard at the end of it's travel.
The 6465K7 shock travels up and then slowly stops at the top no matter how fast it is rising.
BTW, I used 2 as 'working shocks' on the doors during the build and then recycled them onto the engine deck lid by reducing the gas even more. I used 4 of these on my car.