William Sommerwerck wrote:

HiFi AM is stretching the definition of HiFi! Designing and building
a good receiver is not a trivial task. When I was a kid in Jr High and
didn't know any better I used whatever was at hand or I could scrounge
and most projects usually worked, and even worked better when
certain parts were substituted by trial and error. But in reality none
compared to the war surplus receivers I converted.

Last year I sold an old (but never-used) Sony stereo AM radio (for seven times
what I paid for it). Checking it out, I located a local stereo AM station.
Tuning was tricky -- you had to find _just_ the right spot. But had I not known
it was AM, it might very well have thought it FM. The sound was _that_ good.
Certainly hi-fi in the subjective sense of low distortion and coloration.

FM has a major advantage over AM that can be summed up in one word -- limiting.
You can get perfectly flat response without having a perfectly flat IF strip.

I am not sure you know what you mean here.
The FM IF limiting is done to remove all AM from the 10.7 mHz IF signal.
The only information is the frequency modulation.
Foster Seeley FM discriminators are sensitive to AM which causes distortion.
So makers use limiters prior to the FSD.
Ratio Detectors are less prone, but slightly higher thd.
The 300 kHz BW of the 10.7 mHz IF channle is needed because max deviation
in 10.7 mHz is 75 kHz each side of 10.7 mHz.
Such bandwidths allow carrier modulation F up to around 100 kHz,
so several multiplexed signals can be applied to the FM carrier.
The receiver can filter out L+R , 19 kHz pilot, 38 kHz L-R subcarrier,
and another two carriers at 67 kHz and 96 kHz, each of which may
have 10 kHz of audio BW.

Patrick Turner.