when you say tank ... that usualy means springs

search for Accusonics Springs and DIY
http://www.accutronicsreverb.com/

ESP - Elliott Sound Products - Project 34.
Spring Reverb Unit For Guitar.
http://www.sound.au.com/project34.htm

PiAA
http://www.paia.com/ProdArticles/hotspuse.htm

for a DIY plate reverb the obvuous one is at
(dead link removed)
Tape -Op but hosted at Prosound Web

I think Frank has a reverb here somewhere
http://www.nrgrecording.de/diy.html

Ask at the Lab
http://www.groupdiy.com

Thanks Kev!

Great links. I think this should get me started.

I also found an old Tape Op article that discusses building plate reverb as well. Not sure if anyone else on here is interested, but here is the link:

(dead link removed)