Have questions need a lil help
 

Ok first thanks in advance I have 1997 PS f250 crew cab automatic 4x4. I am wanting to rebuild my front axles. I've tore into my axles and found out my plastic thrush washer on both sides are broke along with my cam assembly and wheel retainer keys. My question is this where can I get some better upgraded parts at? My truck is bone stock and would like to get a lil more HP and a lil mileage out of my tanks. I am getting almost 500 miles out of both tanks and I have 382009 miles on my engine. Would it be werth it to do some upgrades? And were can I get better axle parts