I think 4 high in 1st gear. Low range might cause a problem since it will have to shift a lot. 1st will give you enough speed and even if it redlines it won't be there for long when that weight starts moving up and when it does you'll have the power to keep pulling.
If you build up enough speed maybe manually shift it to second but you might not be there very long and just have to shift back down.
And as far as throttle I would just ease into slowly until you end up floored about 10-20 feet from the start line.
Don't forget to let some air out of your tires. And if it starts to wheel hop don't push it you'll surely break something.
Post a video, sounds like fun, wish they had more of those here in Phoenix.
I'm running stock size AT tires. I was thinking of letting the air down to 12 pis.
This event is for the county fair and is just for fun. There is no fee and only door prizes for participants. I thought it would be fun to see what she can do.
As stated if the front end starts hopping let off and you're done. If you don't whatever the weak link in your front end it will do you in. 12 psi sounds low but I don't know enough about those tires. Don't forget you'll be supporting the weight of the sled too.
I ran the tires at 25psi and traction was great. I did not spin at all. I ran 4Hi and 1st gear and powered out at 141 feet. Only the 700 hp trucks were spinning. I should have used 4Low and 2nd. I was lots of fun. I learned a little, and nothing broke on my truck. Not everyone was so lucky. One old Bronco tore the pinion gear completely out of his rear end. One truck broke a rear driveline. There is a video posted on my facebook page but i don't know how to get it here. Just look for it there. Paul Zumpf