Early A V8 Engine Mounts
Tha K-frame in an early A is the same for all but slant and V8 engine mounts are different. If you make this swap you will likely also need the steering center link and throttle cable/pedal from a V8 car. Some have managed a small block with the slant center link but YMMV.
As info, this swap into a 62 or 63 will have issues of enough elbow room. The heater box is a no-go with a SB. 64-66 does not have this issue.