Is this a stand-alone setup, or are you wanting this engine to integrate with the vehicle? (Like a/c controls?)

I believe the 05s used the ecm to enable starting the vehicle. You can probably get cranking voltage from C2 D11 in the underhood fuse block. Cranking doesn’t mean starting. More things need to be happy in order for the engine to run even though it is cranking, but this may be the next step for your project. You’re on the right path with lt1swap.com for a project like this...lots of good swap info for more of a stand-aloneish setup like yours.

I know now you don’t want to hear it, but if your were using an 03-06 harness and ecu you could have almost just plugged it in and started it.

The yellow wire is the start request that goes to the ecu. The ecu then decides wether or not to start the vehicle. I can’t remember, but with the setup you have you might be able to start in gear or something like that. You might try it. On the pre 03 starting conditions are all mechanical, but after 03 that’s all evaluated by the ecm...I could be talking out my ***! It was a long time ago I helped a guy trying that combination.
on the 03+ there is a lot of information that is communicated to the Vcmor on the CAN...your 99-02 does not have that capability. You are getting to the complicated part of how much of it do you want to work. You’re going to make some sacrifices or add some gauges or have some redundant systems in order for it to work both ways.