A different orifice will have an effect on cooling but it's due to the pressure change across the orifice.
The compressor choice will affect the volume of gas being moved, how much energy it robs from the engine, and how long the compressor itself lasts. The old Harrison R4 is not noted for longevity and it's a fairly small displacement compressor compared to the Sanden 508 & the old Harrison A6. The A6 is old, heavy, and eats a lot more fuel to run than the 508.
You have several different things under your control when you charge the system that affects the temps inside the evaporator and the amount of heat energy the refrigerant moves.
You're charging with a refrigerant that the system was not designed for...
I use the JungleEddy method for charging the system because it seems to yield consistent results no matter what I choose for refrigerant. However, it's not entirely a recipe. There's some skill involved. That's why I called it a dance.
Unless someone suddenly changed the basic gas laws I learned in high school chemistry the published pressure to temp relationship of each of these fluorocarbon refrigerants should be fairly static and follow the table and the graph I plotted in Libre Office Calc as a visual using values from the table.
Boyles' law and Charles' Law are the ones I remember as pertinent...
http://chemistry.bd.psu.edu/jircitano/gases.html