dssur
+1y
I did a stock floor on mine, like you I had only done traditionals. The way I did it was not the way everyone else seems to do it, but it worked really well for me.
I pulled the cab and bed off, left the motor and tranny and driveline. I made sure and marked all the gas lines and plugs, even took some pictures. Funny thing, I wanted to keep the A/C charged, so I took the compressor off and zip tied it to the inner fender, when I lifted the cab off it stayed completely intact and charged. I left all the interior in too, just unbolted, unplugged and lifted. Well, me and 6 friends (good friends I might add haha)
I built a jig out of 2x2 metal that went under the stock front lower crossmember and was exactly as wide as the orginal rails.
Once I had the jig aligned under the original frame, I shimmed the frame rails to make the setup perfectly level. Remember that the front cossmember hangs about 1/2 inch lower than the frame rails. This is what gives mazdas that ghetto lean (front slightly higher than the back) that I personally cant stand. So I shimmed the frame rails up about 1/2 inch so that the lowest part of the truck was still the front crossmember.
I welded the front crossmember to the jig, and used four supports, two welded between the core supports and the floor, and two welded behind the front suspension to the floor. These keep the front frame supported once the rails are cut off. I put a similar support under the rear of the tranny, and unbolted the crossmember. I pulled all the brake and gas lines to the front for the time being. I cut the exhaust just behind the manifold.
I built small outriggers off the jig at each of the four factory body mounts. from these out riggers, I stuck a rod up through the center of the body mounts, then cut it off flush with the top of the body mount. This gave me the exact position of the body mount, and gave me the stock height of each mount too.
Then I cut off the frame, first at the rear, removing the axle and driveshaft, then at the firewall line I had marked. I lifted the cut parts off and put them in the dumpster. Except the carrier bearing mount, and I cut the factory tranny crossmember mounts off the frame. Why rebuild whats already there?
I laid the new 3x2 rails in, sticking them at least 3 inches inside the old rails and using the 2x2 jig as a guide to keep them straight. I built body mount, uh MOUNTS and , reusing the factory rubber mounts, held them 2.5 inches LOWER (measured down from the top of that rod I put up through the body mounts) and just welded them in.
I welded in the tranny crossmember mounts, and rebolted the crossmember to it. I added a center crossmember of 2x2, and notched it for the exhuast using some angle iron (two l's make a c!) I welded in a carrier bearing crossmember and reinstalled the carrier mount, rebullt the rear frame section and used the length of the driveshaft to figure where the rearend went. I built and installed my own 4 link too, but thats another tech.
I ran the gas and brake lines and welded the mounting tabs to the new rails. I ran a straight exhaust from where I cut it to just in front of the rear, one easy bend done by a muffler shop.
I dropped the mounting ears of the core support to match the body drop, and notched the lower crossmember for the lower radiator hose.
The cab dropped back on and I could see right through every mount hole. This is what frame builders call "a good thing", it means everything lined up exactly. Done done done.
A lot more work than a traditional BD. I had never done anything this intensive before, and it was kind of scary seeing half the truck out by the dumpster. But if you are logical, you can work out any problem, like when the inside of the stock frame is less than 1/8 and you burn through half of it trying to weld to the new rails lol.
Even though the stock mazda frame is only 5 inches tall and the rails I used were 3, it actually worked out to a 2.5 inch body drop. Remember the front crossmember? You made the new rails even with the bottom of the crossmember and gave it that extra .5 inch. If you roll the pinches under, you lay flat rocker. And no ghetto lean either, mine lays flat the fuck out.
You fit better in a stock floor. And when you get in or out, you feel like you are really on the freakin ground. I'll never own another traditional.
Pics of the process in my profile.