You'd spend more having it certified with a new GVWR than just going out
and buying a dually...
Going to commercial class tires/wheels will gain more tire capacity, but the
RGAWR and GVWR will still be the same...and...have to go through above to re-certify
In going to a dually conversion using commercial class tires will gain you
higher tire capacity and the biggie...wider track. Along with 8 sidewalls
rated commercial class
Agree...your front axle a spindle will need to changed out to the right
offset if the wheels are NOT dually offset now