What size(width) tire can i use for this application?

yea i know..but right now i'm having a hella time trying to get this thing aired up. i see some similiar on ebay..i wana keep it cuz its real..sly, if you will. but if push comes the shove i'm going to have it bored out big enough to put a regular valve stem there..but i hope i dont have to.

SO...9" WIDE WHEEL + 45 OFFSET + 18" WHEEL + 88 TOYOTA PICKUP = SEX