Yeah. This is only my opinion based on what I know, but for reference I'd have to guess that the stock mount, w/it's large rubber bushing and it's air gaps, would rate somewhere between 50-55 durometers. That's my impression after doing the mount.
The 70 is quite a bit stiffer than stock, and I can only imagine what the 88 must feel like. I wouldn't do that one unless I were drag racing the car.