Hey I would definitely go with Ford Motorsport gears, they are by far the easiest to install because of good quality control. You can get these at Diversified Ford or Gene Evans Ford for around $150 which is the cheapest I have ever seen. The Gene Evans site it
www.gefracing.com. If you're not too worried about gas mileage go with 3.73's otherwise the 3.55's would be my next choice. Good luck!