You will not slip your SBC DD at your power level unless its damaged (once its engaged that is)

with 33" tires and a 6spd use 4th gear, 4 low. you said you can hit about 3500rpms so that should be right about where you wanna be. point your drivers side mirrow down so you can see your rear tire, once you tighten the chain and get the green flag, take it up to 3500 or a lil higher if it will free rev that high and once you hit that magic number start to ease the clutch out. you will feel and hear it load the motor and when the truck squats and slowly starts to turn the tires watch your mirror, when you can see about a half rotation of the rear tires you should just about be off the clutch and the tires will break loose and you can go to town, keep the hammer down and dont let out unless it starts hopping.

do not drop your rear tire pressure, keep about 60psi in them they will have plenty of traction with the sled pulling them down into the dirt, drops the fronts to 25-30 depending on track conditions. not enough rear air pressure leads to the bunny hops and broken parts.

here is a video of what i am talking about with letting the tires turn about half a rotation before you are all the way off the clutch, just watch the dirt start slinging. ive done it this way on 27 hooks now and the clutch still holds....gotta love them SBC DD's

 

I am disappointed, I don't think I am going to be able to get it done in time, things fell through on using the shop, But I am also trying to fab some custom stuff, I just got started too late to go this Saturday...

 

I pull in 4-low and 4th or 5th