maybe this will give some reality to this idea- a 225/30/20 is 25.31 inches tall and 8.85 inches wide... a 245/30/22 is 27.8 inches tall and 9.64 inches wide i don't see an isuzu laying frame on these (22's)but good luck.. i mean on one hand it doesnt seem too hard because if i remember right the bed rail on my door layer is right about 25" tall just tall enough for a 20 in the rear so i don't see how a 22 would come out of the bedrails on an isuzu laying frame (should be like 31" tall best guess cuz mine's bd'd 6") With that in mind it seems like it wouldn't be impossible but i don't see it happening anytime soon
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http://www.1010tires.com/TireSizeCalculator.asp?action=submit ) also heres the only price i found... pirelli 245/30/YR22 are 411 bucks a piece