Probably is possible.
Probably not worth it though!
It will make a nicer sound, and will save having to buy replacement filter elements (possible fuel savings as well, but the risk of insufficient filtration for dusty conditions), but I doubt that it will really liberate extra power.
For the 1116cc engine (round air cleaner), you would need a strange-looking adapter plate, or perhaps you could modify the standard plastic housing, fitting the cone over where the temperature-sensing flap is installed, and leave out the paper filter element. Not worth it IMHO, the temp-sensing flap is more likely to improve driveability than the cone filter ever will.
For the 1108cc engine (rectangular air cleaner) - same as the 999cc engine - do a search for 'K&N' and refer to the engine belonging to Chas (1986Uno45S).