"It ran much better". You couldn't undersell that point any more if you tried, LOL.

FMJs have two problems: they've been overlooked forever and there is near-zero aftermarket support. You need to be very skilled, very patient, and very committed to the task. I've owned six M-bodies (including the above-mentioned car) and two J-bodies (Mirada and Imperial) and they are a great platform for a build that just doesn't have the aftermarket backing of other platforms. My late-B Charger has more options.