[dohcpower]

The only reason I would think the northstar swap to be harder is because the 4.6 DOHC is physically larger than the 5.7 LS1...

 

[dohcpower]

I say forget the costly engine swap and just throw a 50-75 shot on there, as well as custom headers, 3000rpm stall torque converter and you will be set. You will have one strong V6 and probably the fastest Catera around...

An aftermarket torque converter really wakes up any auto car. This will increase your off the line quickness a lot. You can have a custom one made from http://www.protorque.com. It will probably cost around $600 but it is well worth it.

 

[dohcpower]

I just found out that the Catera has a 4L30E tranny which is kinda rare as far as I know. So this will have to be a truly custom job, which is still worth it imo...