drill MAF for bigger injs?

I've never heard of drilling a meter to try and fool the calibration. I would imagine that if you had a flow bench you could alter the housing so that the transfer function was correct but I doubt that you have one.

Before all of that though....

Why do you need larger injectors?
Why are you trying to run high impedance injectors?
Do have a high impedance driver to run them with?

Ok... I'll start with your stated plans:

Throw your 24# High Impedance injectors (if they are actually high imped) in the garbage or sell em on ebay.

Long tube headers.... check They're always a good mod and will scale well with your other plans. Plan on getting a Mini-Starter to go with that if you want the option of ever replacing the starter without having to jack the engine and drop the headers.

Get yourself a wideband O2 meter and an EEC tuner (your choice on brand but make sure it's something that YOU will be able to use).

Go straight for 42# injectors. That way you only have to buy them once. 42# injectors will scale with your mods all way through block splitting HP territory.

I wouldn't waste a whole lot time and effort in an intake until you know what heads you're going to run. Price out a good set of aluminum heads in the 185cc territory. Get some roller rockers, match the new combo to a good intake, and purchase a cam to tie it all together.

To hell with underdrive pulleys. For what? If you take the serpentine belt off completely, you'll gain 6-7 RWHP and likely cause cooling and charging problems. For a 20% under drive? Meh.

If you decide to eventually run NO2 with boost, then you'll need to tune for NO2 and boost. Otherwise... BOOM. You can pick up the remains of your motor after you've come to a complete stop.

Folks occasionally get away with installing 42# injectors and a meter calibrated to work with the stock EEC but I wouldn't count it. Regardless of what MAF you run, the EEC has no idea what the minimum and maximum pulse with is for a 42. As a result, you usually end up really rich down low when you adjust FP so that the AFR is correct at WOT.

To do it right, you need MAF meter and the transfer function to go along with it (you would input that transfer function into your tuner).

The wide-band is a MUST if you plan to do all of this yourself. If your running a dry shot, you have no way of knowing if you're even in the ballpark under spray. With a wet system and the recommended jets you're probably in the ball park but you won't know how close you are. The wide band takes all the guess work out.

I don't know what the AFR-1388 is but I can tell you that cam selection is the lynch pin that pulls your combo together. Personally, I would not toss an OEM cam underneath a new set of heads, intake, and MAF. I'd get with someone that really knows cams (i.e. Ed Curtis), fill out his combo sheet, and have him select the cam that will maximize your combo. We're talking about a LOT of lost HP when you run a cam that doesn't suit your build.

Pistons and internals... I'm with ya. Especially if you're planning boost and/or nitrous.

As for a tuner well... There are as many flavors as there are in ice cream. Determine you level of experience and ability to tune. One of the easier tuners I've dealt with is the Anderson Ford Motorsport PMS. You can have your buddy drive the car for you while you read your AFR meter and add or subtract fuel on the fly for your RPM and throttle position, etc. Version 4 will also allow you to input the MAF transfer function and adjust min/max injector pulse width for the size injectors you have. The downside... it's pretty expensive.

The alternative would be to put the mods together and have it chip/dyno tuned. They can always reprogram your chip for your next mod (for a fee +dyno time) but it's the best solution if you have no idea where to even start with digital tuning.