Who's running NGK ZFR5N in there Slant?

I also have the HEI conversion, so I gapped them a bit higher in the 0.036-38" range (and you can certainly go higher).
I am not running HEI conversion (yet.) Mine are gapped approximately between 0.030-0.035" and looking at the spark plugs I appear to have been running a bit rich even with a NOS carb mostly leaned out with limiter caps. I just discovered my voltage regulator appears to be bad and disconnecting it appears to drop my idle speed a bit (which is fine because with the apparently bad VR my idle speed seems to be a little high sporadically 800-950..then 900 through 1150 at steady warm idle. I will tinker with idle after VR replacement then see if maybe I need to increase spark plug gap?

The plug tubes act as the spacer between the plug and head.
Anyone please make sure you clean your tubes as well.

FYI - these plugs are the latest Dan Stern recommendation (he's tried a lot of them).
No specific tuning specifications. If I recall these spark plugs are for medium temperature range medium performance range.