Cutting axles

8 3/4 in 68 Barracuda... Im tipping Im going to have to go the green bearings now but I want to trim 3/4 to an inch off each side to accomodate wheels..Is there a rule of thumb of how much can be removed without issue..Been looking for a how to but that doesnt really explain the axles,Is there a how to for this?...
Im an Aussie ...I know new ones are cheap ish in the US...but not for me,given the exchange rate and the freight is a killer