There are 2 types of shocks available for our cars. Mono-tube and twin-tube. Mono-tube is what you want.
Mono-tube designed shocks have better control, are more firm and have a higher cost to manufacture.
Twin-tube are economy shocks and what were what our OEM shocks were.
Monroe does not make a mono-tube shock for G Body cars. KYB does. The KYB Gas-a-just line is a mono-tube design and is available for all G-Body cars. It's also the least expensive mono-tube designed shock on the market. It's a pretty darn good shock too. Not as good as others out there but all the others are going to be significantly more expensive.
Don't associate "more firm" with "worse ride". If your car is pretty rattle free, a shock that is more firm can actually feel like it rides better than a softer one. A shock with superior control is better at keeping the tire's contact to the road more consistently. It's better for performance too.