We are probably going to be switching over to XML in 2.0 becuase dat/scn files are messy and annoying. We'll probably do a dat to XML converter too.. Plus we can make a nice editor to make game editing stupid simple. 2.0 wont' be out for awhile however...
But to port over dat/scn from 1.2 if you have them at all, theres a tad of additional things you have to do which can be found on the SF.net website, buts its messy atm. If you can get it to 1.2 dat/scn I can convert it over to 1.3.5 in 10 minutes.
The new website will be alot nicer though for understanding what has been done, everythings in the air atm

But basicly 1.3.5.1 is just 1.2RC7 coding thats been modified to solve bugs and a few new features people wanted.