Me personally? I would make an access panel in the pontoon (on a GT40 that's what they call them). If you go that far then make the access panel to take the newer seat belt mounting plate. You don't have to use the factory retractors. You can change over to the comp seat belts.
If you look at the space left between the seat belt and where the roll bar has to go, you may as well convert it.
Get some other opions. Don't just base your decision on what I say. I'm still mezmorized by the girls in George's hot tub and the buttery nipples. (:
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