Need help finding a mid or subwoofer for this box...

[djtomczak 5]

My dad has an old Jensen box that had an 8 inch woofer and a 2 inch tweeter in it, it sounds great but the woofers surrounds are worn away now. I need to replace the woofer in it but I'm having trouble finding one to go with the tweeter, fit in the box, and match the rms of the amp. The tweeter is 8 ohm, the box has about 4.25 inches of space, and his amp puts out 75 rms at 2 ohms and 50 rms at 4 ohms. He needs this for rear fill and to add some bass. This is for his work van so I need to use these enclosures as they just fit behind the seats. If it helps the original box handling was 75 rms at 4 ohms.