ok here is the guide to a 1/2 ton solid axle swap, i will include all parts as well as costs to the best of my memory, as far as i know i did it on a fairly good dime. This swap replaces the stock 1/2 ton independent front suspension axle commonly known as TTB (Twin Traction Beam) with a solid or straight axle from an older 1/2 truck or bronco, most common donor vehicles are 78/79 model year but mine is a bit different
there IS metal fabrication/welding involved along with a fair amount of steering/suspension geometry
heres the parts list for my build keeping in mind very few builds are identical.
i used the 1975 axle, it came with drum brakes, i replaced those with disc brake setup from a 78 axle. I use the 75 axle because the housing is actually stronger than the 78, but the 78 is a more direct and straight forward build.
--1975 dana 44 high pinion 3.50 gears from a 75 f150 4x4 including radius arms + brackets, and lower coil spring buckets
--1978 knuckles and spindles to replace the drum brake knuckles and spindles of the 75 model
i spent a grand total of $400 on this stuff because i had to buy 2 new spindles
heres a good tip, i used the radius arm brackets from the 75...use the ones from the 78, they help with pinion angle, rad arm angle, and are easier to mount.
--1978 brake calipers and hoses (the 75 axle had drum brakes, had to replace those) the TTB calipers WILL NOT fit
--i used the hub and rotor and lockout assemblies from the old TTB axle
--i also needed the caliper brackets from the 78 axle
i bought brand new calipers and hoses so this was about $150 total
--78 4" lift coil springs
--i kept the old TTB upper coil buckets but you can use the 78 buckets, this way you can locate them further forward for a better approach angle, or lower for more lift
--78 trac bar, modified, most people build them from DOM tubing
--1978 tie rod
--custom built drag link, a drag link from a 92-97 F350 4x4 will work, or build your steering
--4* C bushings for rad arms
--trac bar bushing kit
--rad arm bushing kit
so that is roughly $900 not including the lift for the rear end which was another $800 LOL
now onto building the new axle BEFORE you start your swap. To do this swap you must lift the truck at LEAST 4 " via coil springs. Now that you have lifted it you need C bushings, to get the correct bushings while the axle is not attached to a truck is difficult, ask around, someone has lifted their SAS that much too and knows the proper C bushings to use. I lifted 4" and i used 4* offset C bushings to keep positive cater (a good thing). The proper caster measure is about 4* ( positive cater means the axle is rotated clockwise from horizontal when looking from the driver side) caster is measured from the flat spot on top of the knuckle. you want about 4* of positive caster so that your pinion angle will be at its best meaning you want the drive shaft and the pinion to be in as straight of a line as possible. different lift requires different C bushings to correct the caster and pinion angles...also you want your radius arms to be parallel with the ground to optimize movement, this is not a major issue but it does need to be decent, this is why from lifts over 6" you need either longer rad arms or drop brackets, since i used a 4" lift the stock brackets worked
now that you read and understand that you can move on, once you figure out all the bushings and get them, put the axle together (bolt everything you can onto it...rad arms, coil springs ect.)
removing the TTB...6 bolts, 30 minutes of work, self explanatory
no SAS is complete until the TTB is saluted on its way to the scrap pile
now hang the solid axle by the coil springs, once this is done place a jack under that axle and lift until the truck starts to come up off the stands you have it on...be careful with this, it can get squirrely fast, try to find a way to keep the axle under the truck, once the springs are at their compressed ride height, line up the rad arms and brackets on the frame, square everything up making sure the brackets are the same side to side. then mark the holes, drill and bolt them down, once the rad arms are bolted down the truck will stand on its own weight but keep a good eye on it and some jack stands under the frame just in case. now is a good time to mount your shocks and brake lines while the wheels are off. and bolt up the drive shaft, if the pinion yoke on the diff does not match fit your drive shaft just swap in the old one from the TTB
now you have to set up your steering and trac bar, the trac bar keeps the axle under the truck while steering/flexing suspension. the drag link of the steering and the trac bar have to be as close as possible in length and as close to parallel with each other as possible. just because you lifted doesnt mean you will need a drop pitman arm either, wait till after to see if you need one. before you measure everything make sure the axle is square and centered with the truck, then bolt up the tie rod and drag link, measure the length of the drag link and find a location for the bracket you will make that allows the trac bar to be as close to that length as possible, AND as close to the angle of the drag link as possible. then build the trac bar and bracket to suit. this is where the fab comes in, that end of the frame is boxed so most people just weld their brackets onto the frame, also to make the trac bar clear everything you will likely have to cut the front of the engine x-member off and reinforce it however you choose, i dont have to, mine works without cutting it up. install the trac bar and make sure everything is still square, centered and aligned.
DO NOT leave you bracket like this, i still have to add some braces to spread the forces, leaving the bracket like this will likely crack the frame, this is not done in the pic, but its the only pic i have so far
now you sit back crack a beer and admire how much better it looks that that hunker TTB
then take it straight to an alignment shop and have them align it to 1978 F150 4x4 specs
then you TEST IT and ENJOY IT
if you have any questions that were not answered above, ask away.
have fun and good luck with your SAS