I'm going to intall 1.75" front coil spacers. I know that extended bumpstops are probably not required with this amount of lift, stock shocks, and 285/70R17 tires, but I've been told that if I want to run longer shocks, I would need longer bumpstops. I don't know if I'll ever change the shocks, but I was thinking about installing extended bumpstops now, just in case, so that I don't have to pull the coils out a second time. What do you think? How much longer would the bumpstops need to be? I'm thinking about 1", but I'm not sure.

 

The rule of thumb is :
Bumpstop Height = Lift Height

It will depend on the specs of the new shocks, but at a guess, you should be fine with 1" ext stops.