[c-nsp] L2TPv3 - which image for 7200? 7100?

[Neal Rauhauser]

   I have to do an L2TPv3 link (hoping it can move entire 802.1Q streams)
and I'm puzzling over which version of IOS is best. I have a 7206 /w NPE 300
on one side and a 7140 on the other, would like to use the same code on
both.

  And where the heck can I get schooled on the plethora of trains available
for the 72xx series? Years ago there was a Cisco Press book that covered how
this stuff was done - has that been  updated, or is there some sort of FAQ?