If you are just running 30's you can use a 90mm Lightning Meter. They are only about 80 bucks if you shop around. If you need more room to upgrade the SCT meters are best, but more expensive. You will need a tune with any meter you install.
Although IMHO you will want to go straight to the SCT- BA2400 . You wouldnt be able to tell a difference now....but its max power potental is MUCH higher than the lignting maf its based on. Basically, if you decide to up the boost quite abit, the L MAF may not be up to the task even on you stock motor....the BA 2400 should support around 700RWHP in a draw through setup...but in your case with a blow through, it should take in excess of 600RWHP before the meter pegs. Only down side is that they run like $275 .
The MAF is either placed before or after the supercharger....blow through or sucked through. In my opinion a MAF should always be blown through as to get the most accurate readings.
Technically to calculate what size injectors you neeed, you should calculate your fuel consumption (BSFC - Brake Specific Fuel Consumption) first. This can be done by datalogging on the dyno with appropriate loading. You will need to know the RWHP and injector duty cycle. Then you must convert the RWHP to crank HP to perform any fuel calculations. If you can't get the car on a dyno, you can just plug a 80% duty cycle into the formula to obtain a minimum size injector based on that duty cycle to play it safe. You don't want to go over 80% DC especially on a power adder motor.
(Crank HP*BSFC)/(# of injectors*duty cycle)
For instance you wanted to know the injector for 700 RWHP. Let's just assume this is on a manual and we are losing 15% through the drivetrain. That is roughly 824 crank HP. Let's also assume we are not able to get the car on the dyno yet. N/A v8's are normally pretty close to a 0.5 BSFC, 0.55 for N20, 0.55-0.6 for a blower motor, and 0.6-0.7 for a turbo motor.
So (824*0.6)/8*0.8)= 77.25. A 77.25 lb/hr injector should be large enough. Just keep in mind that these are rough calculations when the actual BSFC is unknown, but they will get you pretty close. This also assumes that the new injectors that you install are flow rated at a fuel pressure that is very close to what the stockers are. Most late model Ford specific injectors are flow rated at 39.15 PSI.