I installed the LS1 fans on my '01 5.3 w/28" rad using the NELSON harness. Worked great. Worth the money. Use conservative numbers and just say the mech fans take 12 hp to run. Then use just under 1 hp to turn the alternator for the electrical fans.... you do the math. Also the elect fans will turn on and off when needed. The mech clutch is an approximation.

Just do it!