I got these tips from drccentral.com

Step 1- Begin by disassembling your suspension and stripping everything off of your suspension arms. Even though you will be replacing your blocks and hubs it is advisable to hang onto all old parts anyways. Your phillips head suspension shafts that secure the blocks and hubs to the arms wil also be useless, b/c of the threaded section near the head. Measure the length of the stock phillips head pin, and make marks on your new plain shafts (refer to picture below), and cut the plain shafts to the length of the phillips pin with a dremel tool fitted with a cutting wheel (Wear goggles and be careful with your fingers!).





Step 2- Now we prep the new Pro 4 hubs. The suspension pins used in the Pro 4 to secure the hubs and blocks are smaller than the 3mm thick pins the Sprint uses, so it is necessary to bore out the hubs (refer to the pic below). The 1/8 size drill bit is slightly larger than 3mm, so there will be a small amount of play in the suspension shaft when installed into the hub- this will be corrected with setscrews (don't worry, the setscrew holes are already pre-drilled into the hubs and blocks, so no need to drill this too). Bore both the rear hubs and both of the front C-hubs as well.



*Note* You will notice in the picture that there are 2 spacers pictured, when you assemble your hubs with the bearings these spacers will be sandwiched inbetween the bearings inside the hubs- without anything filling the empty space between the bearings inside the hub, pressure is placed on the inner races of the bearings when the wheel nut is torqued down tight. What essentially happens is the inner races pinch the chrome balls against the inner edges of the outer races... you might have to read that a couple of times... and will result in added friction when the setup is assembled. In a stock Sprint, this is not an issue because the wheel axel is allowed to float, but what this amounts to is a large amount of lateral play within the wheels which will translate into twitchy handling and the car not wanting to track straight. The Pro 4 hubs will allow the wheels to be held much tighter and thus have less play, but at the same time not cause this pinching that will cause bearing failure, high efficiency.)

Step 3- The Pro 4 hubs are slightly narrower than than the Sprint's stock hubs are, so once you do the initial mock up of the assembly the hub will have a good amount of lateral (from side to side) movement on the newly fabricated suspension shafts. To correct this on the front, you only need to use two 3x6x.75mm aluminum spacers on either side of the C-hub. The rear will require one 3x6x2mm spacer on one side of the hub (refer to picture below), and a 3x6x.75 on the other (refer to picture below). The spacers will provide a snug fit and may require a little sanding of the hub at the contact point of one of the spacers to assure a perfect fit (as it did in my case). Its important not to oversand, a snug fit will eventually loosen with regualr use of the car, and will eventually be the perfect tolerance). Also notice the set screws in the middle of the lower part of the hubs. The hub on the left in the picture below had to have the pre-drilled setscrew hole sanded down, due to the fact that there is a 'ring' that protrudes out and will contact the outside of the A-arm (the area that needs to be sanded is in the red circle in the picture below)




Step 4- Now that the suspension shafts have been cut to size and the hubs have been bored out and fitted to accept the spacers, mock up the hubs onto the arms with the suspension pins set in place and the spacers on. There are setscrew holes pre-drilled into the hubs that will secure the suspension pins, but to make sure the setscrews do they're jobs and firmly retain the pins during cornering, we will need to prep the surface that the setscrews will conact on the suspension shaft. With everything lined up the way it should be, stick a needle through the setscrew hole in the hub and scratch the suspension shaft so you will be able to tell where you will need to sand. After this has been done on each shaft, remove the shafts and either sand or notch them where you see the needle scratches. This assures that everything will line up for final assembly with the setscrews.

Step 5- Now that everything is completed (spacer in place beween the bearings inside the hubs, hubs bored out and sanded to appropriate width to accept spacers, and the suspension pins cut to the appropriate length and notched for the setscrews) you can assembled the arms. The last and final step is to insert the wheel axel, connect the dogbones, and screw ball studs into the new hubs for the turnbuckles. Congrats! Now you have a cleaner looking, completely adjustable and lighter suspension setup that will also improve your steering due to the fact that your hubs will now allow your bellcrank to turn the wheels to their limit!