How far off can frame dimensions be? GM A-body

[Nicks67GTO]

Ive got a 67 GTO. Ive been working on a new boxed frame for the car because the old frame was butchered years ago during a "repair".

Anyhow the new frame I have for it is about 1/4" off center to center on all 3 centerline X measurements and about 3/8" off in the middle frame rail where its supposed to measure 53". It measures about 53-3/8". Other than that its about spot on according to my old factory drawings. The ball joints are within 1-2mm after some straightening according to the frame shop so the front end geometry should be really good. The frame is also very level according to the frame shop and verified with my 6' level. Anyhow, the guy there {who has a really good rep for old car frame work} said that the 1/4" off on the 3 X measurements is about what should be expected for a 45 year old car and that the middle mount point isnt really a big deal if its off a touch. He then said that most of the frames were probably off a touch from the factory anyhow.

Im just worried im not going to get this thing under my car as ive never swapped a frame before. How much wiggle room do you have under there when it comes time to swap? Do the mounts have wiggle room or do these #'s need to be spot on to make it work right?

[astroracer]

All you can do is center the tires in the wheel openings and hope it goes together. An 1/8th inch a side isn't bad though and it sounds like it is within tolerance. If you have to do a little grinding on the mounting holes that won't hurt anything.
Don't pay too much attention to the mount locations, get the tires centered front to back and side to side then make the mounts fit that orientation.
Mark

[ChevelleNV]

I have been dealing with Chevelle's for years and seeing a frame out 3/8 is nothing..the mount points all have some wiggle room and you should have no problem mounting that frame to the body. In fact the last frame I did on my current Chevelle project was about 3/8 wider in the center and I had no issue getting it mounted. the only issue I had was I had to file the bolt holes on the trans cross member a bit to make the bolts slide in.

[BMR Sales]

Those old Frames not put together by Robots can be all over the Place. When we designed our Torque Arm Kits for the 1st & 2nd Gen F- Bodies, we had to factor in the various widths of the frame sections ( we measured quite a few cars).