Fun weekend project. I've had this bass since I graduated high school in 2000, and I recently bought a vintage Modulus to replace it. So I decided to turn it fretless. My local luthier wanted $400, and I thought that was too expensive. I couldn't buy an off-the-shelf P-Bass fretless neck, because this Japanese made "Lyte" model was discontinued in the early 2000s and the neck pocket is 1/8" narrower than a standard P-Bass (and anyway they cost ~$250 plus you still need to do a set-up). So I decided to do it myself.
Here's the before:
Took the neck off, ripped the frets out, and gave it a rough sand:
Glued some thin strips of maple veneer into the fret slots (I chose maple so the lines would really pop against the rosewood):
Trimmed and sanded the fretboard with 150 up to 2500 grit:
Finished it with linseed oil:
And then bolted it back on with a new set of flatwound strings, no set-up required:
Plays beautifully, and only cost me about $80 ($50 in supplies plus $30 for a heat gun and a pair of flush cut pliers).