Thanks again Taz.

A clarification, though it's not actually material: The transmission/TC is actually not from the donor pickup. It's assembled from rebuilt 70's era components. I'm not overly worried about that, however.

Also, I don't care if I have to replace the S10 MAF with a Silverado/Sierra MAF/IAT. I just happen to have an '03 and know it doesn't fit the '07 harness, and figured out that it's because it's a combined MAF/IAT. I hadn't really thought it was likely that the '03 tunes or the '03 MAF would be usable, but I was definitely interested in whether there were any reasons an '06 tune might not work on an '06 PCM.

So under the 'You wish to either', I think it's more a matter of wondering if any of those options are safe. You've given some very good specific reasons why each of those are likely not to be safe, so I'll play it safe and get a later 4.3L PCM.

Your comment about time and money is spot on... though through the magic of forums like these, sometimes we can help each other avoid the pitfalls. So thanks for your help! Something had made me hesitant to go buy a third PCM with two sitting on my shelf... I think it was more about the waste than about the cash per se. But with a good reason not to trust them, I've got no reason getting something else.

I'll go to my local wrecker and get a PCM and MAF.

Thanks everyone for your help! I may be back for help once I start tuning... the truck is a mid-engine forward-control van layout, and the V6 is stuffed into a tunnel that was made for a non-cross-flow 3L straight six. So the intake and exhaust is not going to flow as well as the Silverado, and I'm sure I'll need to do some tuning to get everything running like it ought to.

Cheers,
Dave