Trying to convert my old CO2 Shark multi caliber to PCP

Hello dudes. First time posting here so I'm sorry if this goes in another place. 

I have a very old, but still legendary in my country, Shark CO2 multi caliber rifle. The thing is really powerful for a CO2 rifle and as you can see has a huge tank. Anyway, CO2 isn't that great (too sensitive to temperature changes and low pressure compared to PCP), so my idea is replace the CO2 tank with a PCP one. ¿This can be done? I think it's a non standard tank but the idea is use it with a 7,62 barrel instead of the 5,5 or .16 standard ones it had, to have an idea of the power I need.

Sorry for the potato quality



1547242032_3995697315c390a3003f127.17879853_IMG_20190111_182414.jpg