Everyone is trying to make this too hard. Jack: I hope you have solved this by now (but not with wood, hockey sticks, etc).
The 614 vertical vulcanized motor mounts are a monument to poor design.
The 1930 407 4 cylinder cars made in the California plant used a different, much better rear mount. It is shaped something like a cup with a rubber insert so the rear bell housing cross member sat in the rubber cups. When I got my 614 it had the same broken motor mount problem as your 614, so I made use of what I had: I simply took the 407 rear motor mounts from my 407 parts car and bolted them into my 614. Problem solved, easily and with no problem.
Due to low production of the 407 (Durant Motors claimed only 6 cylinder cars would be made in 1930) it may be difficult to find 407 rear motor mounts. The California plant did make 407s so there were a limited number made there. I do not know if any other factories used this motor mount in any of their production. Norm may have some visibility on what the Canadians did for their 4 cylinder cars.
I am surprised no one else mentioned this solution to you because I have shared this info with others over the past few years.
Can't help you there nor can the US / Can aftermarkets. Index says Mountings, Engine Rubber .. but page calls them Engine Rubber Insulators and only shows 1928 / 29 models. Guess the W8A, 22A, 32A ones didn't wear out. If hockey sticks work for roof bows, seems good for engine mounts grin.
Since we invented the 407 which was somewhat copied by Oakland, you would think same mounts but we know each plant did its own thing, like 614 spear handles at Oakland and our own handles at Leaside, and other difference's, so maybe not same mounts as Oakland ? Reg Bent turned a 407 from BC into a 614, he might know. Reg sold all his cars / parts and moved down east.
Where Are You From? Ottawa Ontario Canada
Do You own a car built by Durant? 1932 614 sedan made by Dominion Motors