GTSBoy

So, when did the brakes become spongey? After you did that?

Don't buy "refurbished" MCs from eBay. You don't want a kit. You don't want a mechanic. You want a brake specialist, exactly as Kiwi said. You take YOUR MC in there and they fix it, and they give you a warranty. If you take it home and install it and the pedal is still f**ked, it is very much more likely that you've got another problem, not that the MC is still faulty. And then you start to think about your caliper seals, etc. They can and do, but that leads to a hard pedal, not a mushy pedal.

These discussions are hopeless. The OP is from the US. So the first task is to work out what is meant by "wheel horsepower" anyway. It would be safer to start by specifying that the power wanted is 30% or 50% or some other% more than stock. With the knowledge that stock power was originally 187 kW at the engine (or whatever it actually was on a vanilla 25). But one thing we do know is that RB25s will handle being run at close to 100% power increase for many years. That's a step up from ~140 rwkW (as measured on a typical Aussie roller dyno) up to somewhere between 260-300 rwkW. If the OP's 450 - 500 HP numbers are US inertial roller dyno numbers, then the upper end of that range is in excess of the believable safe range, and the lower end is probably close to the top of the believable safe range. If the 450 - 500 number are engine HP, then it's a piss easy walk in the park.

I have an R32, so no triple gauge to start with. But in that location I have EGT pre-turbo, boost and oil temp. I consider those to be a sensible selection that will tell me most of what's going on. Could obviously add several others, but wouldn't want to make the car look F&F.

No. Not feasible. Go below 5mm at your peril. More is better.

Just measure the diameter of the barrel and subtract 355mm from it to see what radial space is left. (and of course, divide that by 2 for the number you're really looking for). Then you can ponder which calipers will fit in that gap, and if perchance there was room for a 5 or 10mm larger disc as well. Oh, plus the running clearance you're happy to live with.

Yeah, nah, I don't believe it. Try to use a thin screwdriver blade to lever the blue plastic + glass out of the original one. I bet you those terminals come right through the plastic. But notwithstanding my scepticism, you're looking for something like these, yes? https://www.ebay.com.au/itm/Air-Con-Climate-Control-LCD-LED-SMD-Light-Upgrade-For-Nissan-Skyline-Stagea/161839873383?hash=item25ae687d67:m:mNBLDEFYdzn8tzeIYklj5RA

Um, the plastic bit is not replaced when you change bulbs. You just push the globes/leds into them.

Up there with the pie floater and the yiros/souvlaki.

Money no object + brilliance.

Meaning you have checked that there is power on the pin(s) that are supposed to have power, earth on the pin(s) that are supposed to have earth, etc? Have you tried to power it up on the bench?

It depends on the calipers you use too. Different calipers have different radial "height" over the outer edge of the disc.

Low compression won't make it run rough. That will be something else. Dirty injectors, faulty coils, AFM, CAS, IACV, etc etc. The usual suspects on 30 year old Skylines. If you have the money, rebuild it. You'll need ~$5k just to get a rebuild that you won't be ashamed of done though. Nothing special, mind.

Have a look at photos of the two gearboxes. You will see why one cable is shorter than the other. The speedo cable connection point is in a different place. Also, I suspect that the connection at the gearbox is not the same either.

But you weren't wanting to install it on the car, were you? It's just to put on the shelf so you know you "have" it while you use a decent ECU on the engine itself, right?

The whole argument on Rotella is probably a waste of time anyway, if we work on the likely assumption that the OP is in Australia. It's not sold here, AFAIK.

Why not put the effort in to do it properly?

Dim sim is definitely the cheaper end of the scale, but only because it's actually almost an Australian thing, not Chinese. In China the whole category of dumplings is known as dim sum. One particular type of dumpling is the Aussie dim sim. Dim sum would be part of the food offering at a typical yum cha.

All the more reason not to use a "fixed" ECU.

What do you mean "Trace my VIN"? Your car's ID plates will be in the bottom of a scrap metal bin and the rest will have been used to repair another car.

How stock is it?

Hmm. I had a look through the entire manual and could not see a representation of that plug either. I'd suggest you're down to following the wires.

The wiring diagram is a thing.

The crank would have to push the piston all the way through the combustion chamber and into the valve seat area to hit a valve that is closed and cannot be open because there is nothing (no camshaft) to push it open. Close eyes. Picture inside of engine.

No cams installed = ........ [you complete the sentence].