Is this the right tool for the job?
 

To remove spindle locking nuts for rotor removal 90 3/4 ton 4X4
http://www.powerbuilttools.com/cdimages/648475.jpg

I know
 

thats what you use on the older trucks (70's). but have never had a newer one apart. Bet theres not much difference.

That looks just like the one I bought recently to remove the hubs on my 72. If I remember correctly, the packaging indicated it was for GM vehicles. If that is the case you should be good to go.

Not 100% sure about the '90, but all the front axles I have seen use the smaller 4 prong socket. That looks like the one for a rear ff 14 bolt.

Now that I think about it, mine does only have 4 prongs that key into the locking ring. The one for Ford's may have had 6 keys.

So is it 6 prong or 4 prong? I believe the front end to be a 10 bolt corporate with auto lock hubs. Before i start the work i want to make sure i have the proper tools. The Napa guy said the 6 prong is for ford and chevy 3/4 ton 4x4 but i want confirmation.

The one I bought at NAPA was for GM vehicles and had 4 prongs. I remember seeing one for Ford's that had 6 prongs. There were no date specifications on the packaging. I would think your's would take the 4 prong. It doesn't take much to get things torn apart down to the locking ring to verify. If you want to have it on hand before you start, I would go with the 4 prong and if by chance it is not correct, you can always return it and get the one you know you need at that time.

Just a warning, mine was around $23 and I think the 6 prong one was substanially more.

As the other guys have said I'm not sure for a '90 but for my '79 it was a four prong tool. I was looking at buying one to and it was the same 6 prong one you had pictured. I made my own.

i dont know about the front axle but the rear FF on my truck is a 6 prong

My 85 10 bolt front axle used the 4 prong type. The same tool also fits my 70 dana44 8 lug axle also.

Ok i guess its gonna be the 4 prong, let the work begin. Is the first step well after the wheel is off to remove a big spring clip and spring? my chiltons doesn't seem to say that, but it looks like i have to remove locking hub stuff in order to get to the big locking nut. Any place on the web the will give me a step by step or should i buy a gm manual. I thought i was mechanically inclined but i don't want mess up the auto hub stuff just want to put new rotors and pads on.

When I did mine a couple of weeks ago, it was the first time I had ever taken a manual locking hub apart. It is pretty straight forward especially once you get all the parts out so that you can see them. I was following directions in a Haynes manual and it was very accurate as to the parts and steps that I had to follow. Make sure you closely follow the directions for putting it back together. There is a set proceedure for torque on the locknut when you reinstall.

Good Luck.