what kind of spacers would be best

[AKADriver]

What are the exact specs of the wheel (diameter/width/offset) and tire that you're running? Coilovers normally reduce the inboard side clearance but most people nowadays run such low offset wheels on their cars that they never notice. But if you want max tire width between the coilover and fender lip, spacers can help dial that in.

Extended studs are no big deal to install, a worthwhile "might as well" if you're messing with the suspension anyway.

For slip-on spacers the quality is less of a concern since it is basically just a big washer. Hubcentric ones are convenient since you can just slap the wheel on and zip down the lug nuts but also not necessary. I have Kyo-ei generic multi-pattern spacers because I'm running non-hubcentric wheels (well, they're Mitsubishi hubcentric at 67.1mm so 1mm O/S for Nissan anyway) and they work just fine. No vibration, no loose lugs. But I always run the lugs down by hand, torque in a star pattern, final torque on the ground to ensure the wheels are centered.

I'm not a fan of bolt on spacers for an S-chassis application for two reasons:

1. Most importantly: good quality ones cost as much as if you had just bought better wheels that don't need them, or if you're 4 lug and just couldn't find good wheels, if you had just bought a set of 5 lug hubs and opened yourself up to a plethora of cheap 5 lug wheels.
2. They're usually a minimum of 20mm thick which is just too much spacer for the kind of offset setup I personally like for my driving style and conservative visual taste.