Allow me to update the soap opera.
So, I could kind of see how things were likely to go as I did the work. All the headbolt holes showed evidence of oil getting in. Some more than others. The ARP sealant is, of course, a thread sealant and according to the packaging it doesn't set. I could kind of see after doing the first one that it was fairly likely that on a small surface like the washer and bolt head it would be prone to washing out. Well, but then I don't understand how something like that survives on threads in a non-blind hole without washing out. So, I dunno. At least it gave me an excuse to do the retorque on all the other headbolts I needed to do.
In any case, started and warmed it up and... Yup. Smoke. Took it for a drive just to rule out the smoke being from pooled oil from earlier and... Yup.
Measured the bolt holes. For the benefit of future searchers it looks like a 1/2" hole. Well, my calliper made it 33/64" or 1/2" plus 1/64" or 0.516". So it looks like the sleeve I want is the .500 one. Jegs want like $60 postage. Both Summit and Jegs won't ship til end of August. The drag and drive event I'm booked in for is mid-June. Anyway, after trawling across the internet I eventually found a model supplier with the identical 12" long .500" diameter .014" wall brass tubing. Hopefully here some time next week. I measured the hole depth on the head (it's easy to do from the side of the head) and it's basically a tiny bit longer than 3" like 3 and 1/3 or something. So cutting that tube in four equal pieces will yield me 3" lengths which should be perfect. Just hope they fit close enough to be sealable with threadlock and don't pinch the bolt. I assume it will be fine because it's the exact dimensions of the one Dart sell as a "head bolt sleeve"...
Stay tuned. If it's not this... I dunno. God give me strength!
Sam