I've used the Wynns Radiator stopleak product before, and found it works really well, it stays fluid so can never block up the cooling system, but can be flushed out once you can afford to fix it properly. It also works well as a preventative to seepage around hoses caused by antifreeze.
I'm running 175lb springs with an a series and even that feels stiff considering factory is 90lb. I guess it comes down to how much suspension travel you have and how you're going to drive it.