E-450 and E-350 tires are the same size. I made reference to your comment about the F-450, not E-450. Hope that wasn't a misprint, or that I was too confusing on that -- was typing too fast.
Years ago I think Ford offered 4.10 and 4.30 gears on E-Series (back when I had mine). More recently I think it's either 4.10 or 4.56. Obviously if you are changing the ring and pinion set you have even more choices.
My points about gearing is that spacing between gears plays a major role overall, and that's not usually taken into account as it should be in the bigger picture. I understand you are talking about roughly a 5% change, but how is that going to affect overall performance when gear spacing can be around 50% (more or less) with your 5-speed transmission?
Anyway, I now understand what you want -- hope you get it.
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