On LS1tech.com website in the 'Conversions and Hybrids' section there is a sticky with all the different oil pans available for the LS motors.
Here's the link-
https://ls1tech.com/forums/conversio...-oil-pans.html
There is also quite a few build threads there detailing LS installations in our trucks and you might want to look there for what others have used for headers. if you are using a M2 suspension and an auto/non stock pedal, there should be several options for you.
Id sure modify the firewall and position the engine such that some off the shelf headers would work. I'd even consider an intermediate steering shaft support if it would avoid custom headers.