Welcome Brian.
What is your actual goal?
Another good place to come up with ideas will be the IS-F forums. That engine is the most similar to yours and at 5.0 liters making 416hp = 83.2hp per liter. Your LS460 has 4.6 liters making 380hp = 82.6hp/ltr. For equal performance per liter you only need to gain 3 horsepower!!!
Interestingly your 460 has 367lb/tq @ 4100rpm vs 371lb/tq @ 5200rpm for the IS-F. That means you have MORE torque per liter vs the IS-F with 79.8lb/tq per ltr vs 74.2lb/tq per ltr.
So, the mods for the IS-F should give similar gains for your LS460. Higher flowing intake/air filter designs, better exhaust manifolds/headers less restrictive mufflers (= more noise).
The LS460 AWD has a slightly higher gear ratio AND the Torsen "limited slip" differential at 3.133 vs your 2.937 which MAY be tolerated by the electronics (maybe not) but would give about 7% more rear wheel torque. This can add up because you take the engines torque (367 less drivetrain loss so lets say 300) times first gear ( 4.596 ) times the differential ratio ( 2.937 ) gives an impressive 4,050rwtq in 1st gear. With the 3.133 that increases 7% to 4,320rwtq. BTW, these are fairly accurate numbers. In 6th gear (1.00 ) the difference is still 7% but is much less (obviously) at 881rwtq vs 940rwtq respectively.
I have not seen a torque converter upgrade but sending a stocker to a good company like Precision Industries may lead to an interesting option.
USUALLY overlooked by those whating MORE power is improving the power to weight ratio of the car. This is the same as making more power with the existing weight. The best way I know would be lighter tires and wheels as you gain both in absolute weight loss as well as reduced rotational mass... both make you quicker. Weigh the stock tires and wheels, shop for FORGED lightweight wheels and compare tire weights (they vary).
Looks like the IS-F guys are having some luck running nitrous which may be your best option if occasional power is your goal.
If you want to get carried away it is probably possible to swap the IS-F 5.0 liter into your car, stroke that motor, turbocharge your motor or a bigger one... how much do you care to spend???
