The depth (8.75”) of the stock truck oil pan is often an issue. The most common swap is to the “F” body (camaro / firebird) oil pan at 5.5”. They can be found on Ebay, LS1Tech, Corvetteforum, and other Forums in the classifieds or from GMPARTSDIRECT.COM for $242. The shallowest pan is the Kevco LS F-Body “gated” pan at 5” deep. A remote oil filter will be needed with the Kevco pan as well as their specific pickup. Try to use the factory truck oil pan unless all else fails to save you some money. Here is a great link to many different oil pans with dimensions & part numbers: LS1Tech-Oil Pans
The engine will have the factory positive & negative battery terminals attached to it. It connects ground to the engine & chassis, and routes the positive led to the starter motor & alternator. It generally has one other smaller gauge wire that can be used to power the rest of the vehicle. It is usually located on the front drivers-side of the engine. You can use it, or route your own battery cables. It is NOT part of the engine run harness.
Water Temp Sensor
There is a factory ECM temp sensor on the drivers side head towards the front. An additional sensor for an in-cab gauge can be located in the same port of the passenger side head, towards the rear. Here is the metric to 1/8” NPT adapter: ATM-2277
The ECM (engine control module / computer) is mounted under the hood in the factory truck or suv. It is completely waterproof and is easiest to mount there. Although you can locate it in the cab it is not necessary and a large hole in the firewall would be required to pass the connecting plugs through. M & M Offroad and others make brackets that can be helpful as well.
EGR System Removal / Blockoff (If obtaining your own 1999-2001 Engine)
The EGR system generally needs to be removed unless you need to meet SMOG requirements. Simple block off plates can be made to cap the exhaust manifolds. I find it easier / quicker / cheaper to use the parts from the factory system, cut the tubing off and weld the holes closed and bolt back on. You can use a large rubber cap that will go over the tubing on the port in the manifold or a factory plug is available for about $15 – GM Part number 12558346