Ok , need to step back

I picked up a 70 Duster last year as another project thinking I needed another car. A year
later Im finding out that may not be so and something has to go. The Duster would be a fun build and I have done alot so far like replacing left rear quarter and installing
GTS pulges on the hood plus all the cleaning and sanding but there still alot, ALOT! of time work and money. The Dart is finished but has a 470 really not MPG friendly and I would like to be able to cruise away from home and the fact I have some seperation issues with the Dart. Sorry this is so long I need to sort it out. Heres what Im thinking. I have a built
340 for the Duster. Im thinking of pulling the
470 and swapping in the 340. Sell the 470 and Duster use that noney to upgrade Dart .
Thoughts?