3 Multi-Leaf Add A Leaf Kit - Which would be better???

3 Multi-Leaf Add A Leaf Kit 1.5" HD - Which would be better???

I just ordered this for my 2006 TRD DCSB 4x4.

My question is - I was told without overload spring - I would be getting about 1.75" lift? How much lift would I get if I left the overload spring in???

Plus - I will be towing a 6,500 boat from time to time. I have read a couple of threads, that say the overload spring will help with towing?
I mostly do 90% pavement driving!!! ( So not really looking for better off-road ride. ) I wanted the 2" AAL - but was back-ordered for 3 weeks!

Anybody having this setup, I would greatly thank you for any advice or how it works with or without that spring...

 

I got about 2" with the overload left in with the Icon 3 Leaf Pack. The ride is not anywhere near as harsh as I was told it could be too.

 

Thanks.. that's exactly what I am looking for...