Find a NOS RCA 6L6 Blackplate; that will help the little sucker
overdrive a bit more, especially if it has a crummy OEM
Chinese 6L6.

Just as an aside, if you want to make it louder for those small
club/pub gigs put a JAN Philips 7581A in instead of the crappy
OEM chinese 6L6 that most left the factory with. MUCH better
tone and lots more headroom.

What I did was add RCA jacks for the reverb send and return. I
tried a few full size tanks I had around. The best sounding was
a 17" 3 spring. I cut the tank down to 15" as well as the spring
assembly and shortened the 2 loosest springs slightly. I put
this in a bag and recalibrated the reverb. The calibration
instructions are on the schematic. 

The original reverb is in a small cardboard enclosure. When I
opened it up I found one of the springs disconnected. Hooking
it back up the original sounded much better. 

The problem with this design is it is speaker driven. With this
scheme the reverb drive is taken off the speaker, the return is
pumped back into the amp. The reverb is "recirculated" with
this design. There is a calibration pot that will increase the
intensity of the drive, but set it too high and the reverb will
feedback, and it has an unpleasant, metallic sound. This is a
weakness of this design. It just won't sound like most Fender
reverbs.