F,M,and J's not created equal. I know the some of those had much worse bumper issues than later M bodies for example. The bumper fills got better too as did end fills. Same on R Bodies. They had some quality issues that were much better on M's. The '88 and '89 M's at the end of their run were pretty darn good. Still 80's cars and there weren't any big three that were much better. M's got more galvanized steel in '85 and pretty darn durable. Only thing missing was EFI and there was plenty of problems with that and many preferred carbs.
The problem with the M body was the simple fact they were 4 door cars. These days, its much easier to convince a young driver that a 4 door car could ever be a performance car. Back then, 4 door cars were grandpa & grandma cars, real performance cars HAD to be 2 door cars. A 4 door could be a "sleeper" which was fun for a while, but not something you wanted to keep, and certainly not something you enter car shows with.
I bought my son a very nice 87 5th Ave for his 1st car, around 1998. It had a few tweaks and could run pretty hard, but he hated that car, even though it was a great car. His friends made fun of him for driving grandpa's car (even though nothing any of them had could run with it even while it was hauling 4 big guys).
At the time, all of the 2 door F & J Mopar car line up had poor trim pieces, huge overstuffed sofa style seats, and nothing performance rated. Both the 318 and the 360 were pretty wimpy power plants in factory trim, and poor rear gear choices and lock up transmissions that were locking up at 25 mph sure didn't help. The closest thing to a performance car was the B body Charger, if it had a big block. Sadly the big block wasn't on the option list for either an F or a J body car, that probably would have changed everything.
A couple pictures.
pic 1 My F body dirt track car. in this pic, the car was 3 weeks old, and junk. This was the good side! A guy came up along in left side and caught the front bumper as he was going past me. Him just catching the front bumper caused the driver side front frame rail to pull 4" away from the transmission crossmember. That was the time I decided I wasn't cut out to be a race car driver. The 1st week out I blew up the 318 (strictly stock class), the 2nd week it got squished between two big boats, then the 3rd week the chassis pulled apart. As for my cloths, I'd just got off work from my factory maintenance at a forge shop, my cloths pretty much looked like this at the end of every day. The time frame would have been around 1983. That 76 Road Runner was already a bad rust bucket, the guy gave it to me to race.
pic 2, My other toy at the time. This pic was probably taken at the 82 Mopar Nationals.
