OEX LXA119 Alternator 12V 65A Lucas Style Volkswagen Speaker Adaptors You could also use this

You could also use this amp bridged in one-channel mode to power a subwoofer with up to 240 watts RMS

2 x 150 Watts @ 2 Ohms

OEX LLX33043 Specifications:

or behind cab panels

25W x 4 RMS Built-In Amplification

OEX LXA119 Alternator 12V 65A Lucas Style Volkswagen Speaker Adaptors You could also use thisOEX Alternator 12V 65A Lucas Style OEX LXA119 Features: Has W terminal for tacho output OEX LXA119 Specifications: Adjusting Hole Diameter M8x1. 25 Inside Mounting Legs 83mm Pin Code IR165 Pivot Hole Diameter 8 Power Rating (Amp) 65 Pulley Outside Diameter 66mm Pulley Section A Regulator Type Internal Suits Unit Make Lucas Voltage 12 Note Has W terminal for tacho output Alternator Mount Twin Leg Mount Cnt to Cnt 148mm New Reman. New Shaft Dimension 17