Big Block or Small Block in my 70 Duster

The intention is for this to be a street car - flirting with the idea of the 440 because I have a fresh one in the garage! I may just hold onto that for a while and rebuild one of my small blocks. I've got a solid 360 core and a 340 with X heads. Might be easier on this since this is my first car build - put together a few trucks, but time for a car now.

Are the SS springs a bit on the stiff side?