This one in a nice Torino red/competition stripes finish has been up FS for ages, I assume (1) as its been modded for a P pickup and (2) as its a bit overpriced. The modding might not bother you, given you were happy to mod your 60s Mustang, perhaps? And I bet they would take a significantly lower offer, given how long its been sitting there. Edit: the link doesn't take you directly to the bass but if you scroll down to the one FS at Guitarzilla, that's the one.
https://reverb.com/uk/p/fender-mb-98-slash-mb-sd-mustang-bass-reissue-mij