You are likely going to want to run the 18lbs if you are expecting to put down 400hp at the rear wheels. Does the 7m come w/all of the supporting mods for the 400hp?

A couple 100lbs of sand or a water bag over the rear axle should help fix the traction problem.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed