LAB SERIES L5 (jazz)

So I decided to give my old Lab Series L5 a last try before I put an X on it and get an (expensive) Rivera Jazz Supreme.

I am the original owner of this amp that I bought in 1980 and used it on the road for 5 years.  Its been collecting dust for 30 years. 

First thing i'll be doing to it will be to fix the reverb (hope its only a tank issue).  If i can get some decent reverb out of it, I'd like to replace the original 12 in. speakers.  Any suggestions ?  I'm looking to get a clean jazz tone out of this amp ; something comparable to the Rivera Jazz Supreme.

Thanks for any suggestions.  Richard

ps: the guitars i'll be connecting to the amp will be either a Gibson ES335 (1979) or a Godin MultiAcc Jazz or a Godin 5th Avenue Jazz.

https://wgs4.com/search/node/LAB%20SERIES

Sounds like the G12C/Ret 30 is a real winning combo :-)