Got the engine mounted to the K-member and the transmission attached.
The motor mounts listed on RockAuto.com, eBay, and elsewhere on this site (Anchor 2266, DEA A2266, Westar EM2266) did not work for me. I can't see how they could work.
The funny thing is that mount is recommended for Darts with 273 V8. But Valiants and Barracudas call for a different mount (Anchor 2338, DEA A2338, Westar EM2338). I picked up a set of the DEA A2338 mounts and things went much better.
Now I can really start moving forward with assembly.