@KevinCarson1 suppose that's 225.
225x8: 285
235x8: 298

Adding 10lbs requires 13lbs more strength.

Your 5rm should be about 245. If you add 5lbs to that: 292. You only need to be 7lbs stronger.

The laziest, slowest way is to add a microplate or such and beat your 5rm by any amount of weight. If it goes up by 5lbs, your 8rm should now be 232. The laziest way is to increase 5rm, up to at most 5lbs.

The laziest way is to, paradoxically, work at higher intensity.