The early Suburbans are a little tricky as the raingutters are
not structural. We have to bolt in "artificial"
raingutters to take their place. The later Suburbans have
factory racks rated at 165 pounds and are very easy to mount crossbars. We have been using the Thule 415 Railing Feet and crossbars or their
new "Rapid Railing" system, both work very well on the
newer Suburbans and Yukons.
The smaller Blazer uses the same system but the rack is rated at
150 pounds by Thule. This isn't a problem as we use smaller
tents that are between 95 to 130 pounds.