[Arran]

There are various ways to handle this, one is to cut near just above that rolled in area is near the bottom, using the rolled in area as a glue joint, this will make the can 1/4'' shorter but nobody will notice. The other method would be to cut the cap off the top, save the cap, and glue a cork to the bottom of it making it into a sort of stopper. Is there a cap on this can or is it all one piece? If it's one piece then it's probably a dry electrolytic inside, basically a "jelly roll" of paper and foil, wet electrolytics have a cap with a vent in it, the can is aluminum in this case, older ones were copper or brass.
Another method, that I have used to repair a crudely cut can, was to put tape around the circumference of the can, and cut or file down to it, on each half, and then use some pipe, or tubing to couple the can together on the inside, though some use aluminum tape, like is used for HVAC work. I would guess that you would want to save the label, so you can cut the can either above, or bellow the label, or better yet soak it in lacquer thinner to get the glue to dissolve, and let go, so you can avoid damaging it, either replacing it or scanning and making a reproduction.
Another way is to bore out the can from the bottom, this is easier said then done unless you have a lathe. Also with a lather you can cut the rolled over edge off the bottom, hopefully releasing the insulated threaded plug, but you can also uncrimp it with a flat blade, or just file it off, then you can extract the innards of the can, restuff, and glue the plug back in, with suitable holes added for the capacitor leads to come out from.
Regards
Arran