I'm going to look at this truck this weekend...I wasn't aware GMC made trucks pre 1935!? Is this a rare unit? http://www.kijiji.ca/v-classic-cars...ck/1005839880?enableSearchNavigationFlag=true
I had a recollection that GMC trucks dated back to the WW1 era. A quick search turned up the info that the first GMC trucks were sold in 1912 and 1913. But, they were made by a General Motors division that had been founded by the Grabowski brothers in 1902 . No it was not called Henway, but Rapid.
According to the info I found on Google (http://jalopnik.com/5968173/111-years-of-hauling-a-gmc-truck-history/), GMC traces their roots back to 1902 and the first truck bearing the GMC name was first used on a truck in 1912.
I guess you will also be looking at his 1926 Durrant Coupe, It also looks pretty cool. Good Luck !!!!!! Larry