I bumped into this thread by accident and curiosity. Back in the old days we used the Isky tool, sure it was expensive back then too but solved the problem. We ran both 392 and 426 hemi on nitro in TF, TFC and alcohol as well as built some motors for boats.

We just o-ringed the block and not the heads. We used copper head gaskets and spay contact cement. 3M stuff. It worked pretty well. It was a real problem to get the heads off if they were on for any length of time but the blown cars had the heads off nearly every week anyway. We also used a bit of silicone sealer around the water holes on those that used water with good success.

I don't remember the exact number but the depth of the groove was about .004 or so less than the wire. We carefully tapped the wire in with a plastic hammer so as not to flatten it. The fuel cars ran a bit more stick out as I recall. I'd guess around .008-.010 as the wire was sometimes hard to get to stay in.