I think this is the schematic (says "Blues Classic" in the title, at any rate).
http://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-Classic50-Schematic.pdfReverb (at the bottom of the first page) looks to be driven, then made up by the two halves of a good ol' 4558 with the amount of return/wet signal being controlled by a 10k pot wired volume control fashion.
My thoughts are that it might work to plug a clean boost into the reverb return without having to go inside the amp at all - assuming there's an rca lead coming from the reverb tank/pan/brick back into the amp to increase the level of the wet signal coming back in.
I think that's what the original poster wants to try - anyone else have any thoughts?