which kernel should I modify?

I am about to start modifying a linux kernel to run on a custom mpc8240 board
that has a uart, boot rom, a pair of amd 32Mbit roms, and a PCI bus.  It is
intended to act as an IP router.

I was wondering, can anyone recommend which kernel tree I should start with?
Should I begin with the standard PPC 2.4 tree or the 2.4_devel tree?

Thanks

			--Dustin

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