Rear seat belt bolts 71 vert

[Xghobo]

Having issues with rear seat belt bolts for 71 convertible, I have and installed C11 bolts but for the outer belt they seem too long. They are 1 1/4 long threads and shoulder with the shoulder being 3/8. I cannot tighten all the way due to hitting wheel well so I have 1 or 2 threads plus the 3/8 shoulder sticking out both sides. Now will this interfere with the rear seat? Also it looks like I should be using C13 bolts which I do not have but are they shorter? Anyone have the measurements of a C13?

[Cuda Cody]

Here's a C13 seat belt bolt...