Don't buy anything that needs mods...modify it to make it better, not to make it possible. Unless...unless you're a tinkerer and modify everything as your hobby. The factory setting on the rear shocks is in the #2 slot...you should use the #5 slot and max pressure in both tires according to the sticker on the bike.
Everybody re-jets the carburetor. That plus a windshield and fork braces is about it.
The S40 is the right size for you, but you might do one modification of fabricating a mount for a Harley seat. The power is limited, but it'll pull you, no passenger, OK, but not with great acceleration. How much acceleration do you need to safely get on the highways and interstates there?
Are you open to an off-topic suggestion?...read
this book.