Slant 6 to smallblock

Looking at a 1974 Dodge Dart Swinger. The car is an original slant six car. The intake and exhaust manifolds have been removed from it for quite some time so the original slant six is most likely locked up. I have had a 1975 360 block, and a full forged kit to make it into a 408 stroker. I have been looking to finish the engine and put it into something for quite some time. I would like to put it into this dart but I am not sure if the slant six to small block mounts will be enough. Or should I change the entire K member to a v8 K member. I know I will have to change the torsion bars to the larger, stronger v8 ones. Should I change the entire K member or should the aftermarket mounts be fine?