First off, I have a 98 Ranger. Second, Is it possible to install amps underneath the front driver and passenger side seats? If so, is this location enough ventilation for an amp. If no, what is a recommended location.
Lots of heavy washers that fit the bolts will work fine and you can use them in increments to get just the rise you need. You can then take the bolts somehere and find longer bolts with matching threads.