5.7 Hemi or Built 340?

I have been planning and building my build of my 70 Dart. I have an all rebuilt 340 with a 3000 stall torque converter and reverse manual valvebody that ran high 12's s in the previous owners Duster. My plan was to upgrade to an overdrive tranny because I have 4.10's in the rear of the Dart now and do not like how high the engine revs when driving 60 mphs. I also plan to get fuel injection for the 340 down the road.
I just got offered a deal of a 5.7L Hemi (62K miles) and all needed accessories still in a wrecked Dodge Magnum in trade for a spare 1972 Dodge Dart that I was going to get rid of anyways. The magnum is AWD, so I will still need to pick up a transmission.
THis car will be an occasional daily driver and maybe a little fun on the side.
Any thoughts?