Run the PSA on the floor next to it 😁
It's hard to not find the distortion you're after in the PSA, it's an amazing little thing. I'm slightly ashamed that mine isn't getting used.
It does depend on the bass - the EBS only really gave that sort of ZZ Top grind with the single coil P. They push drive pedals in a particular way. With everything else it had that typical Billy midrangey sound.
What bass(es) are you using?
Here's a very interesting video on the lined/unlined debate I saw recently. I rarely play fretless, and haven't owned one for years, but I always naturally went to lined. More accurate, surely? Maybe not...
It's not very helpful I know, but the main thing here is the old-style Precision with the single coil. The distortion is adding flavour but that single coil clank is really what this sound is all about.
When I had such a Precision I used to get a great ZZ Top tone with an EBS Billy Sheehan, surprisingly. I don't think chasing a Marshall-derived tone is vital.