Hi there, I'd really recommend going with the 305/40-22's instead as I'm pretty sure you will get rubbing in the front fender wells while turning with the 305/45-22's once lowered as they are even a bit larger in diameter than the 305/35-24's that were rubbing on my truck.
If you want to check yourself there is a good tire size comparison site at
http://www.powerdog.com/tiresize.cgi. Here are the three sizes that I was working with.
Size Diameter
305/40-22 31.6"
305/35-24 32.4"
305/45-22 32.8"
No worries about towing with the 2/3 drop kit as I have used mine for 1,000's of miles of towing a car hauler with about 4,500 lbs total with car and trailer (pics attached).
I actually don't know my drop kit as I did not install it. It is something I am trying to find out as I want to upgrade the shocks to firm up the ride a bit as it is a bit too bouncy for my taste especially when towing the trailer of bumps and dips on the freeway. I know where the work was originally done so am going to try to find out this week if they can look up records as to what was actually installed on the truck so I can figure out what shocks can be added.
Cheers.