if you want, i can get specs on OEM GM ECM/ECU parameters for the SmarTrak system; so you'd know limitations for max lift prior to re-plotting computer.. and you and your uncle are correct; 400HP would do damage to transfer/trans/axles.. you can get your stock drivetrain up to 262-275 HP/TQ before having to 'stout'ening to a heavier set-up..
good luck on the project though; if you decide to undertake..