I'm a little confused. If you are using nutserts, why does it matter what the originals were? You can use any size bolts you want. Why is it critical to use the original Model A bolts, this isn't a restoration ?

I would just use 3/8 bolts and appropriate size nutserts. I considered using nutserts to install the body on my T, but instead cut little square tabs out of 3/8 thick plate, welded them on top of the frame, and tapped 3/8 threads into them. Nutserts should be ok though.

If there is some specific reason why you want to use the model a bolts, let us know.

Don