Octane boosters do very little to nothing, only a lead additive would actually work in such a small bottle, but such an additive would be illegal and dangerous.

Need to know what duration the cam is because "308 duration" means pretty much nothing. The Sweedes had a head porting competition a few years ago, they were using 11.7:1 with Enem's biggest 'street/race' cam which was 272°@.050", 0.315" lobe lift and the fuel used was Shell's Vortec Premium pump gas, 100 octane (R+M)/2 method.

You really need to find out what the cam is, then make sure it's degreed in correctly and has all 8 lobes.

What size are the valves? 106° LCA (aka LSA) Is a bit odd. 46/38mm valves need wider LCA than 44/35, I think Enem do 109° assuming the head is ported correctlty with 46/38 valves. With my 44/35 I go 102° aiming for maximum torque in the 3000-6500rpm range and with my 269°@.050" cam I used my 11.5ish:1 used lead premium on the street with timing locked at 27°, when taken to the track I added toluene and set the timing to 34° locked, but that was the 90's, now leaded fuel & toluene are illegal.

2x45DCOE use 38mm chokes, 4.5 or 5.0 aux venturis and F16 emulsion tubes. If you have a good motor, the mains and air correctors will end up about the same size, If it's a great motor, the air correctors will end up bigger.

I am now ready to start programming the 123 ignition. The notes from the builder show initial timing at 0-5 BTDC and 29-34 at 3000 or above. The 123 wants a full curve. Does anyone know how to go about getting the full curve?

Do you know whether the block was decked and the piston crowns machined / matched to establish a consistent piston height above the deck at the correct height to establish the proper quench zone depth? Overbore B20 engines without establishing the correct quench zone can be relentless pingers requiring retarded ignition or ridiculously high octane. A B20E with a 10.5:1 with correct quench zones will run just fine on 89 octane. It would seem strange that the engine would require something beyond 104 (are you talking RON or R+M/2?).

If you are just trying to get it running, I wouldn't sweat the octane for now. Its not particularly important in terms of getting the engine to at least idle so that you can start the tuning process. By the way, getting a 308 deg duration cam to idle is going to be a challenge. Octane will become an issue when you start to establish the tune for maximum power.

I don't do Webers; but, my recollection is that too much fuel pressure is as much of an issue as not enough. What kind of electric fuel pump are you installing? You may need to install a fuel pressure regulator to control pressure to the carbs and install a return line if you went mungo on the pump.

Unless you have prior experience with Weber carbs and have a good guess at where the tuning starting point is going to be, you are going to be going through a lot of spark plugs as you do your mixture checks. I suggest you get a wideband O2 sensor so you get a sense of where your AFRs are. You can buy data loggers that will record engine speed and the AFR reported by the O2 sensor and that will allow you to make an educated assessment of what mixture adjustments you need to make on your Webers or how big the mixture adjustments need to be.

Agree on the fuel pump--I am told it is proven on DCOE45's. It puts out 60-70 gph at 4psi--so high volume/low pressure.

Weber's are very sensitive of fuel pressure, should be 3 lbs, racing fuel is a must, additive doesn't work you will detonate your motor. 36 degrees for timing, you will have to figure your Weber jetting, every motor is different