My KYB's are on a 70...All front suspension and vehicle weight are nearly the same as the 64. About 15K on them...the gas shocks seemed to improve the handling some as I don't really notice much rollover.
I put Monroes's all the way around on my '63 Dodge. The ride was great! I did replace the fronts only because I wanted 90/10 shock to get the front end up and keep it there for weight transfer. Fronts are now Competition Engineering.
On my 63 Sport Fury street/strip car I run the Comp Engineering 90/10's up front and the MP long shocks in the rear to work with the SS springs. Car drives and rides great. Ron
I used to run Lakewood 90/10's on the front but for my new street car setup I'm running KYB gas units. For the rear I use Rancho adjustable shocks set on 2 for the street and set them on 7 for the track. Gus