The 305 was definitely popular, they stuck them in all the light duty trucks and a great many medium duty trucks as well. I do think GMC should have offered the 351 from the get go in 1960 for light duty trucks. Originally the 305C was slated for being discontinued after 1971 but somehow survived with the last of the V6 engines up to 1974
, being the longest produced of all the GMC family of 60 degree V engines.