you are suppose to gear down 1/10th in gear size for every inch larger you add in tire to keep power the same. stock tires are 32 inches tall. you have 3.73's stock..... you've changed tire height to 37's. thats 5 inches. so 5/10th's gear reduction from 3.73's is 4.23's.....so 4.30's......well add the added weight of the tires so step down to the next gear which is 4.56's......... for the front 8.8 diff, get Ford racing gears.....they are the best gears you can get for that size ring gear.