360 header bolts long tube headers and allen key bolt

Hey, anybody have any good tips on how to get this header bolt on? I don't know if there's a special tool. I have to have to get on but I can't get my hands in there because it's too tight. And the boat has a Allen key top. So I have to have an Allen rich type tool to get in there. But the space is such a small space that I'm not able to get anything in there. Anybody with a part number for a tool? I appreciate it. You can message me back anytime on anybody's and I'd greatly appreciate it. Here's some pictures for reference.

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