Dave Mustaine's signature King V from 1993 had a L500XL in the neck, because Dave could use the blades as extra frets, and the ceramic J-92C in the bridge. I hear a great difference in the guitar tones on 'Rust in Peace' and 'Countdown to Extinction'. Apart from the fact that the band recorded digitally and used different Marshalls on 'Countdown to Extinction', while the tone on 'Countdown to Extinction' was all classic JB, the tone on 'Rust in Peace' screamed more, had far more gain, and was much darker, slightly like the signature Distortion tone, arguing a ceramic magnet. I think Dave Mustaine started using Duncans after the recording of 'Rust in Peace',
Dave Mustaine used his neck pickups for cleans on his albums till he got his signature set, and then he started soloing on the neck pickup. That is still a rare occurrence, but here's one such solo:
Marty Friedman's guitar tone on 'Rust in Peace' is one of my all-time favourites. It was the perfect compromise, because it could handle the heavy 'Deth rhythm tones, and cut through very clearly for solos. It had a warm low-end, an almost EVH-like midrange and a very bright, open high-end with great harmonics. It was bright and clear while being saturated, and had that slight vocal quality to it which made his solos jump out of the mix. I think it was a combination of the rig he used then and his articulation, because Mustaine's soloing with almost the exact same rig sounded different (albeit in a good way), and while his articulation and fingers remain as incredible as they were twenty-four years ago, his rig has that unpleasant darkness and lack of 'sparkle' and 'freshness' which his Jackson-era leads didn't. Maybe it was the radical downtuning. I still haven't found out what pickups might achieve his tone, but I think the IM1, if it was a tad more balanced and smoother, and the Full Shred, if it had a little more low-end, or the Perpetual Burn or A2P, with a little adjustment might get one there.