Yep......actually 61 to 66 Valiant and 63 to 66 Dart K frames are the same all you need is V8 mounts which started in the A-bodies in 64 with the 273. I put a 318 in my 62 Valiant wagon without changing the slant 6 K-frame, you'll have to wrangle a pair of early mounts. I used Spitfire headers on mine, good fit-a fuzz tight on the steering box though, and as stated the heater core box will have to be removed.