The old 'it will ruin the ride' commentary.
So, let's unpack that a bit. Your truck is over 10yrs old with over 100k miles; the replacement with an AMK compressor will probably last the life of the vehicle in realistic terms (call it another 10yrs, 100k miles-unless you really like these things). That said, are your struts new too? How about the EAS blocks? The EAS on these trucks is very robust and reliable, but does age and will encounter problems over time-sometimes expensive problems (esp if you take them to mechanics). I would submit to you that you are in the beginning of reconditioning your EAS, not the end. Which is fine if you need it b/c you tow, or the type of load out you do requires it, or the cross axling is something you truly value, etc.
That said...
-The coils don't ruin the ride. That's just inane. The first question to ask is 'do you have a coil spring D3/D4 to base that opinion on?'
-The coils don't ruin the handling. (for both ride and handling and argument could be made, subjectively, that they improve it actually-esp compared to a clapped out 100k EAS setup)
-Coils don't really do much to mpg. Tire size may affect it a little, but in the end it will be a rounding error-even at CA costs.
Here's more info (also in my build thread but faster to point here:
https://nas-row.com/showthread.php?t=175)
Hope that helps.
r-
Ray