The AMT 62 impala is a nice kit. The Revell 62 impala is a nice kit, from what I have heard 'I dont own one or have built one, I dont like either 63 impala's from AMT or Revell, AMT Prestige series is just old & worn out mold, from what I Have seen kind of toylike.The Revell is based on a diecast,the Engine is garbage.However it can be improved with the Revell 64 impala, if you want a SBC engine, and chassis. The AMT 64 impala is not too bad, it seems to have been around for ever the last one I built was in the late 70's early 80's and its still readily available. Again the Revell 64 appears to have more in the way of detail and could be a little harder to find.
My disclaimer here, these old eyes have seen all of these kits and this is my best recollection IMHO.