Like Mikeo said, just turn it around if it is not a linkage type. If it is a linkage type then you can replace it with a non linkage shift lever pointing backwards. The only problem can be finding a lever that is the right length to match up with your footpeg position. Too short and you lose all of your leverage and too long and it might interfere with a frame tube or casing before you get full engagement of a gear. The other question is will you be able to live with a GP pattern. If you have other street bikes will you be able to make the switch back and forth? Banging a downshift exiting a turn while hard on the gas really sucks. FWIW I prefer a GP pattern for racing and generally set up my street bikes the same way. Don't lend your bike to somebody that isn't experienced with the reversed pattern.
Ken
PS what are you going to do about the rear brake?
AHRMA 412
Vintage racing - old guys on old bikes
Ken
PS what are you going to do about the rear brake?
AHRMA 412
Vintage racing - old guys on old bikes