I just nostalgia'd hard on the G&S Redlines.
Most important question is how much space do you have to work with. The few subs that'll really take 1500W continuous power and sound nice doing it are going to require some mounting depth and a good bit of airspace and port volume.
Chances are a modern high quality 12" in a solid ported box will outperform most pair of 15's sealed you heard 15 years ago on that power.