Converting a crosman ratty 2250 AirSource to single co2

[Shed tuner]

I seem to have come into possession of the above gun. Needs a reseal, but I've quickly realised that whilst I like the metal breach, I prefer just a regular 12g CO2 cart for the occasional use the kids will have with it.

Seems to me that all I need to switch back is a regular valve with piercing pin, and the end cap with the short extension ? I know there are minor stock changes, but that's just cosmetics. Am I right, or am I missing something ? Does the valve port hole in the side of the cylinder cause a sealing problem ? I doubt it as the cylinder itself is not pressurised - the co2 cart just seals against the valve face...?

Thanks in advance,

JB