Well here is a trick a old fella helped my brother with on a 47 International Pickup , he re-did ,
They took Spot Putty in a tube an reduced it with Laquer Thinner an sprayed it on , it had the same pits .
Will take several coats but sprayin the filler gets rid of the air gaps that will let the pits rust again ...this held up for yrs afterwards , and she still looked good last time i saw her before he sold her off .
Just a thought ?