GPZ 750 530 chain conversion/gear ratios

Hi there....new to the group.

Just bought a 82 GPZ750.
Nice mint low miler and all stock other than a supertrapp 4/1.

I want to do a 530 chain conversion.
I also want to gear down a bit from the stock ration.
It is 13/33 for 2.53 i believe.

Q I want use bigger frt and rear sprocket setup like the 83 thru 85 GPZ which used 15/38.

Can I use the 15/38 setup on my bike?
Why did the 82 use 13/33 and the later bikes 15/38?
I would think the bigger front sprocket is more efficient with the gentler chain bend?

I am thinking of going to 15/40 or 41 with a 530 setup.....sound good?

Any and all info on this Q and chain/sprocket/gearing welcome.

Thanks

Check with this Excel worksheet:

Gear Ratio Worksheet