Back in 88 I started the build on my 38 chevy (same frame as yours) I bought a mustang 2 and cut the front end off removing the metal that would be the frame if it had one. When all the measuring was done the 38s frame was 1/8" wider than the opening in the mustang crossmember. A bar clamp was used to pull it together and I slid the two to geather. I rolled the rack with the use of bevel washers. When we set the front end alignment we used the mustang specks. I could take off ramps at 60 and the car just went right around the corner. never had a bit of trouble. BUT I did a lot of measuring before putting it together.