It looks as if you already have on/off ASAs - they have a part on the front that will screw in and out to open and close the pin valve on the bottles regulator
This makes it easier to unscrew the bottle when pressurised, and you can also 'turn off' then shoot the last air inside the gun guaranteeing that it cannot be accidentally fired
You ought to be able to just unbolt the drop forward from the gun and the ASA from the drop forward. Then bolt the ASA to the gun.
The macro lines on each are still long, if they had been cut down then you would need to replace them to put the ASA directly to the gun. You probably don't need new macro line, but if they have been heated and shaped, or have just naturally taken the shape over time then you would need to replace them
Have a try and see how they feel as they are before you go into too much effort in changing - or change over one and compare how they feel.
Are you sorted for goggles, pods & something to carry yet?
If not don't rush to buy them - you can still loan them from sites, and the same goes for an air cylinder if you have not had yours tested by the time you play.
Sites may provide those extras for free or for a basic fee or deposit such as £5 even at walkons - but it's wise to call and ask first