Front spring u bolts

[Res731]

Im replacing the front spring and having a heck of a time getting the bolts on anywhere near enough to get the cotter pins in. Some details.

Reusing the old u bolts and nuts
Old spring was broken so I got a new set from snyders
I used slip plate between the leaves but I don't think it adds much height.
I followed less Andrews instructions and put a piece of webbing on top with grease
I did grind the top leaf edges
Yes, the center bolt is lined up with hole in frame

When installing, one bolt stripped all the threads out trying to get it tight enough for the cotter

How an I tell if I ground enough of a bevel on top row? Any other suggestions, lesson learned? I thought this would have been easier but certainly doesn't seem to be working out.

Thanks.

Rudy