98 K2500, 5.7 to 5.3

[Zukikev]

Hey everyone, I believe I have done a reasonable amount of research prior to posting, but I have some questions I'd like to clear up.

The 98 2500 I'm swapping into has a 5.7 and 4l80e.

Will I require a different flexplate or some sort of spacer? I read about this at S&P (here: http://www.hotrodlane.cc/PDFFILES/Lisa%20Tahoe.pdf )

The LM7 I'm swapping in is a drive by wire. Do I try to work with it or swap a throttle body from a 99-02 truck that is not drive by wire? (S&P write up says get gas pedal and tach module. I'm not sure if I kept these parts from the 03 I got the engine from)

Is a conversion header required? Or will the stock LM7 manifold fit? The Shoenfeld headers won't fit a 4x4 truck but the NITROUS headers will fit a 4x4 truck, is that correct?

I am assuming I won't have to move the transmission and transfercase in the 98. Is this what the conversion motor mount kits achieve?

I don't have a rad. Which is the best one to use, a 96-98 or a 99+? Is there a difference?

Edit* some of my questions were answered so I removed them as they weren't very strong tech