Have you looked at the Tri-Y type that were OEM on the Shelby GT350. They and some "Straight Drop Road Race" type can be viewed @
WWW.CobraRestorers.com. Good source for parts.
The Tri-Y type angle toward the chassis centerline as they pass the parting line of the block/bellhousing. I have a 289 type car and have looked at an Aurora before. The dimensions seemed similar as I recall.
Hope this helps
Rick