Can you route them over the back of the seat, like in between the headrest and the lower section? Lot’s of 4pt harnesses can be routed that way. I figure you’ll need to mock it up a few ways to be sure…
ANother recommendation would be to NOT rely on the stock belt mounting locations, especially for 5pt. Pegasus racing sells clip-in eyelets and tabs for cheap…that way you can optimal placement and instant quick release for the street.