We did the upgrade to Disc brake and the Mor-ryde IS, it's not cheap but worth it, also went with the 8k springs. We have a 3670rl and I think this was the best thing we ever did. The trailer rides very smooth, stuff isn't all over the place when we stop. The 8k may be a little overkill, but we are happy with it, we were never overloaded around 12k on trailer when hitched up was the most we ever had. Being a old trucker I know my weights on axles. Brake wise, once you have disc brakes you'll wonder how did I stop before. Good luck with your decision.