I have owned both a 383 and 340 FS FB. The 383 was stock so heavy. Putting 0.94" torsion bars and a 1 1/4" sway bar really changed the handling. Yes, a 383 with AL heads and other low weight parts weighs about what a stock 340 weighs, but a 340 with AL heads, intake and tubular exhaust is nearly the weight of a /6. I actually enjoyed the 383 a lot as it was a 4sp while the 340 was a 727. But the 340 was much faster as the 383 was the 290 HP version. I did update the cam and ported the heads along with unshrouding the intake valve to cylinder wall, but the 383 still wasn't as snappy as the 340.
Unfortunately, I had to sell the 383 and have no idea where it ended up. The next owner sold it to a third-party weeks after buying it.