255-35-18
It maintains better overall height to prevent throwing your speedo too off and maintains almost identical side wall heights to your rear 295-30-19.
255-40-18 is too tall ( 0.68 inches taller)...
... and 265-35-18 may be a little too wide since you are going from a 9.5 width to a 8.5 width up front.
Lets see some pics when you get'em!
John