Ah, OK - I have one of these, too - still a leftover from the late 80s. The OBL 500 XL is loud though not as loud as the Wilde one, has a lot of high midrange but not much treble. I played the OBL 500 XL for years with a PAF style neck humbucker so basically any type of pickup would work. To make a more distinct recommendation, what kind of guitar is the pickup going in, what are your musical styles, what kind of amp do you play and what do you want to get from the pickup?
Cheers Stephan