When I was at this stage about 5 years ago I had a similar question.
My '46 also came without the radiator springs. I found and had good results with hood fit etc with some after market springs. The bad news is I can't recall the specifics. I have checked my notes, receipts and done a search in the Stovebolt without success. Someone suggested a FLAPS and as I recall they gave a recommended application. I am thinking now it may have been a suggestion in Tim Sheridan's old website???? I recall buying them at NAPA, off a revolving display rack. As I recall, they were for a foreign import--maybe Nissan? The package came with the spring, two packages were needed, bolt, nut and washers. Only the spring was used and SAE bolts etc were substituted.
Does any of this parts info ring any bells with anyone else?
UPDATE:::
I found the receipt and did a search on the NAPA online catalog.
The part number is: 600-3120 --Stud and nut kit.
Hope this helps.