I don't know about the traffic where you live, but I won't risk driving my 66 any faster than 45 MPH with my factory brakes (power drums) because of the spazzes that I have to be constantly watching out for! These idiots will pull out 300 feet in front of a loaded semi traveling 55 MPH and expect him not to plow them down; I figure they must have slept throught their physics classes in school. If they'll do something so stupid to a large, heavy, fast-traveling vehicle I figure they're even more likely to try & take me out in that old pickup truck. After all, it's "so old" that it can't be traveling very fast!
The swap is so straight forward and much safer than the best stock brakes had to offer that I can't see not doing it unless he's wanting a resto (which doesn't jibe with the drop)... safety first or bodywork (or worse!) later!
