Unfortunately no LS truck manifolds fit in between the frame rails that we know of. Some of the LS car manifolds may fit, but we haven't worked with. Other known aftermarket manifolds work, such as:

Hooker 8501HKR
Summit Racing SUM-G9080

Some center-drop headers do fit between the frame rails with some “massaging.”



As for oil pans, for clearance, we have recommended the GM Muscle Car Oil Pan. Otherwise there will be issues on the front axle. The factory LM4 oil pan does not fit at all.
Part #: Chevrolet Performance 809-19212593.

There may be other parts that work - others can chime in.