The one piece canopy's don't bother me as much on 1/72 scale, my eyes aren't that great anymore nor am I have a steady to put lots of detail into this small of a cockpit. I do have a couple of the True Details 1/72 cockpits for the P-40's, don't remember which variants they were for more if they are more generic, but they're not bad.
As far as the tires, treadless is actually an appropriate for this variant, here's a couple photos.
http://www.p40warhawk.com/WW2_Era/Groups/AVG/Rato/AVG/AVG.htm