Eddie, I have had a 3.0l V6 (side conversion with pop top) now for just over a year, I absolutely love it. It has 4 speeds, but only ever use 'D'. for normal driving...I have used 'L2' (have D4/3/L2) but only to get out of a field on a slight incline, and needed the lower revs, and D4 when in the Lakes on Country lane inclines, but for normal driving, it stays in 'D'.
MPG wise, if I'm honest I dont have a clue, but reckon on 400+ miles off a tank (E5) on motorway/A road driving. Yes its thirsty around town, but hey, its a heavy beast...
I went for the 3.0 over the 2.4 as when I test drove both, the 3.0 just felt better. At 65-68 on a motorway, laden with 2 adults I pull just over 2k revs, and she just purrs along.
There will be those that tell you an X is better than a Y, but at the end of the day, its your choice.
What are you using the Alph for, 2nd car / Camper only / Day car ?
This very much dictates what you go for (ive been advised by an LPG conversion specialist) that for the mileage I drive it, its not worth it (do about 4-7k a year max).
HTH