It is believed that all or most T400 laptops are compatible. See notes about CPU compatibility for potential incompatibilities.
There are two possible flash chip sizes for the T400: 4MiB (32Mbit) or 8MiB (64Mbit). This can be identified by the type of flash chip below the palmrest: 4MiB is SOIC-8, 8MiB is SOIC-16.
The T400 laptops come with the ME (and sometimes AMT in addition) before flashing libreboot. Libreboot disables and removes it by using a modified descriptor: see gm45_remove_me.html (contains notes, plus instructions)
Flashing instructions can be found at ../install/index.html#flashrom
The T400, when run without CPU microcode updates in coreboot, currently kernel panics if running QEMU with vt-x enabled on 2 cores for the guest. With a single core enabled for the guest, the guest panics (but the host is fine). Working around this in QEMU might be possible; if not, software virtualization should work fine (it's just slower).
On GM45 hardware (with libreboot), make sure that the kvm and kvm_intel kernel modules are not loaded, when using QEMU.
The following errata datasheet from Intel might help with investigation: http://download.intel.com/design/mobile/specupdt/320121.pdf
The T400 is almost identical to the X200, code-wise. See x200.html.
The coreboot wiki shows how to collect various logs useful in porting to new boards. Following are outputs from the T400:
Copyright © 2015 Leah Rowe <info@minifree.org>
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