Is it possible to buy just the crossovers? I have 2 sets of rokford fosgate 6.5" component sets (don't judge me they were $50 a piece during back Friday locally). They did not come with crrossovers. I have sundown for everything else in my truck.

Why would you want to use something that potentially wont work well for the speakers.

You can not just toss any random passive crossover in with your speakers and expect good results.

If you knew the crossover frequency and slope of the RF crossovers you might be able to find or build a replacement of equivalent values. But just blindly using Sundown crossovers simply because everything else in your truck is Sundown is a terrible idea.

If you want to stay "mostly" Sundown, get a 4 channel Sundown amp and run the RF's active. JPS