I see a huge discussion on internals has taken place...
Nice to see the video above with attention to detail, getting things working right.
Woody, I am not going to tell you what to do, as you must be out of short trousers by now. Consider;
Block, clean, remove oil gallery plugs so can clean, then fit NPT plug. smoothing off the under side of block, it removes roughness for oil drain quicker back to sump, removes cast material and can relieve where stress fractures can occur, esp if you plan at running at 7k. Paint inside. I have done this. Thoughly tap all holes to aid good assembly. Check deck surface is flat. On that note, I have a couple of z owner friends, both have had problems with machined parts that were "flat" when they aren't. This is probably down to the milling machine not been serviced, greased, swarf removed. I have seen the wear on Bridgeports mills, and the state they get into... so make sure flat is flat. What bolts, ARP? What about cooling, change the core plugs, drill out the water holes in the deck of the block?
Crank, check straight, polish journals, a few "free" hp and it has less wear on bearings. Don't skimp on bearings quality, e.g. Nissan. as good quslity is less likely to gaul.
Rod and Pistons, that is up to you, except to say the stock rod is perfectly good for "street" and even race applications. Consider getting them prepped, if not, the very least make sure they are part of a balanced set-up.
Head, some of this you can attempt, do, its not hard, some I have done. Cam, up to you, but consider whether it is ground onto an internal or externally oiled. If an externally oiled system, need spray bar, but you would need a set of appropriate cam towers, matched. It chucks the oil everywhere , and if you are running 7k rpm... Valve springs, are you going to get float at high rpm, what spring pressure, stock, or light...? What oil stem seals..? rockers, do you lighten for valve train inertia...?, what valve hats do you go for? if skimmed, tower shims or Kenmeari tensioner? Un-shroud the valves, will aid flow, but add cc to compression value, valve job, what can/needs to be done? Work out your combustion chamber cc, easy with chemist burette (I have one if you want) and have done. You could easily find when the cylinder head was cast, the dies have "moved" giving you un-even volumes. Can do some of the work here yourself in removing material. Do you weld the combustion chambers up, do you weld up the injector notches in the intake ports. What porting is done? Check thread holes and water passageways, check how head gasket sits, does it line up? What gasket do I go for? Check head flat on 3 sides. No point over-sizing valves, the N42 is already 44mm, any larger and your exhaust port won't cope, and become a restiction. Any valve/seat work, make sure the valves all sit at the same height. I have had a "Z specialist" do mine many years ago, and they were allover the place, so adding lash pads was a faff. Do you mod the head for better cooling at the rear?
Oil pump can keep up with your engine revs, and your water pump. I see you mentioned different rad, but a large % or people don't think of the thermostat, they open at varying heights, so are a restriction.
If using Ztherpy rebuilt carbs (by the way, they can be bored out if too small for engine cc), the N36 inlet manifold (from a 260z) has been said to be better than the 240z one, and add a few hp's. I still think it can be improved further (the N36). Inlet/exhaust gasket, make sure it fits and not cover part of any port, and do you port match? What studs here do you use? Think about how you fit the manifolds, they can be different heights, most stack bits of washers, yuck. I worked and had my intake notched so it was the same height as the exhaust, so clamping force is equal, less likely to leak. I see you mention header, size?
Plenty to discuss, rather than just what over-bore. I personally would leave and concentrate on things like above. A 1mm overbore just on its own isn't going to gain many hp, 3 or 4?.... Unless you go big, my next project, using the original Nissan block/head will have a 70% increase in cc over stock....