GH, I have run mechanical injectors with my stock head. Because of "theory" I choose not to stay with them on gasoline. On the GMC cylinders 3 and 4 are the only 2 with even pulses between firings ie: the fuel "puddles" the same amount of time between those 2. The others 1, 2, 5, & 6 all have either more or less pulses between firings. In theory with a constant flow mechanical injection this mean you have 2 cylinders lean, 2 cylinders rich and 2 cylinders with the correct mixture. Odds are not good enough for me I still need all 6.
This can be masked with multiple nozzles and butterflies and is currently being done with quite a bit of success by a few racers just not yet by me.
The Buick is far worse in my opinion for constant flow mechanical fuel injection. Just look back at the message with the firing order and you will see what I mean. The shared intakes are separated by 1 pulse, then by 6. A lot of flowing fuel to puddle while 6 other cylinders fire.
I run vintage classes only so EFI is not an option. If it ever becomes one on vintage engines you won't see me any more. I kinda like Pro Stock and Nascar for these reasons.
I personally believe the placement of the nozzle on injected engine is dictated by the type of fuel. Methanol and nitro low and gasoline higher. EFI seems to be low on all my modern cars.....Good Luck