Q: Camshaft interchangeability 4.2 & 4.0

Great thread! Thanks for sharing. That helps lend a little more anecdotal input on the fuel pump lobe question for the renix cams. Looks like the safe bet would be to assume that it wouldn't be there at this point, given the stock rotation has bound to have cycled out anything that still had them by this point. Much appreciated!

Yep. 12 measurements total; 3 width measurements at each of 4 equally spaced levels down the depth of the cylinders, in between the ends of ring travel in the stroke, starting crossways to the length of the block, turn 120°, then turn an additional 120° from there (procedure described in the engine overhaul manual). Then I took a separate measurement on each cylinder to check piston/bore clearance (crossways, at a depth of 2.3125"), and it was there where things went sideways haha

Long/short, I was getting a lot of bad reads, partly due to lack of experience with the bore measurement instruments (hard to develop that "feel" with telescoping gauges. Thought the bore indicator would be more forgiving, and it was — just not as much as I needed). Turns out a trip to the machinist is unavoidable, which is a bummer because of cost, but more because of backlog. I have one who I might be able to get the block to on Monday, but everyone else was booked out for months (one has 75 motors in queue and doesn't expect to have an opening until December!). 

When all was said and done and I could get good reads that I had strong confidence in, I had one cylinder that was maxed out for out of round AND taper allowances (0.001 out and the same for taper). Yeah, it was "within tolerances", but not too long after it gets fired up and wear is put on it, it'll be leaving the long blue smoky tail. But it was really the measurements I got for piston/bore clearance that did it. . . Man. Not a single cylinder measured out to under 5 thou out! At that point I had to bite the bullet. Needs a bore & hone and some oversized pistons & rings. Thinking it'll prob need 2 over, maybe more, but I'll trust what the machinist has to say on that. 

Glad you're going to bore it! I was going to ask how long you plan on keeping the vehicle, as not boring now would probably get you 10-30K (depending on all sorts of things!) before it needed it and it would have to be torn down again. Hyper pistons would be nice and are available, but for a basically stock rebuild there's no need. Still, I'd go for them if price isn't much more than standard cast replacements.

Several Jeepers I know (only on internet though) use the 4.0L cam as a slight upgrade from a stock 258 cam. Can't say if it's enough to notice, but cost is about the same as a stock 258 cam so why not a slightly better one?

That's kinda what my thought was, but the considerably lower price was what really made the idea shine. Switching to an electric fuel pump because of a lack of a pump lobe isn't really that big of a problem; it could even save me some bigger headaches down the line, seeing as failure with a mechanical pump isn't just a breakdown, but a breakdown AND an oil change (and would happen right after I put fresh stuff in, because that just seems to be the way it goes). I'll just have to sit down and do some cogitation like with the pistons as far as what the real price would end up shaking out to.