363 is 14", 405 is 16", while 455 is 18". Carbine length guns are 14".
^ Direct conversions
That is the same gun I purchased when I first got into airsoft. The AOE needs to be corrected but other then that as a stock gun I like it. Although now the only thing left stock on that gun is the receiver, motor grip, and front sight.
I personally would get this:
Although I like full stocks on DMR type rifles.
^Both guns are wired to deans if you don't already use deans on your charger you might want to think about getting some deans plugs for your batteries or getting an adapter. I would stick with deans though they have a lower resistance then tamiya plugs and are easier to use.