I beleive the only way you can get one is to have a race manifold guy weld one up for you. Ive run a couple of 351ws and never saw one either. If youre going for speed a victor or jr will make more power but theres nothing like two carbs sticking out of the hood
Here is the link for the 302. Weiand is the only company I have ever known to make them. You should be able to get a part number from weiand and give it to jegs or summit and get it.
What do you plan to run that on? A tunnel ram sucks for a street car. If you put a 351 in a fox and use a Victor or Victor JR intake, the carb will stick out of the hood anyway.
with the right combo and some tuning, it's hard to beat the tunnel ram.. and you can always get good deals on them and carbs... I got a pair of 660 center squirters for $150.. tunnel ram for $80..