i wnated to fit larger tyres on my surf too but when i found out that 265/70R17's (803mm) are 3.48% larger than the 265/65R17's (776mm) i had on already i decided to back away from teh idea as nobody here would have any idea as to how to reprogram the speedo.
then again nobody actually follows the speed limit here, and it's not really enforced either.
not worth a ticket, you're better off fitting 275/65R17's (789mm or 1.68% larger than stock) they'll fit in the spare wheel well too.