360 engine vibration

Hi guys,this might be a little late but I'll share anyway.I was a auto tech for forty years,I saw alot of 360's right out of the showroom that had a bad vibration in neutral and driving too,most obvious in park at about 1500rpm.The problem was the new 360 engine had a cast crankshaft,they just started using them on the 360 unlike the 340 and 318 which had steel cranks.Cast cranks were externally balanced using the torque converter to accomplish this now the converter weighs maybe 40 pounds if it is out of balance it's gonna shake tremendously.I had some cars that I thought the dash was going to shake loose.This whole deal was a design flaw.See if you can find a converter for a cast crank.Oh by the way I'm a big block guy,and I race a 64 Fury.Been a mopar nut since 1970. Good Luck.