For the reverb tank, I would contact Cal at Accutronics in Chicago...actually Cary IL. You can locate their website by Googling Accutronics Reverb. Cal can help you with any reverb questions that you have.
Regarding handles; I couldn find any handles exactly like the original Sunn, so I bought some heavy duty handles from Parts Express....Parts-Express.com. I am very pleased
I've redone a 67 Sunn Sentura II and it had the original Gibbs "F" unit reverb tank. Accutronics, who purchsed purchased the Gibbs company back in the late 60's. makes a Model 4 that is exactly the same as the old "F" unit. I even had my Model 4 built with the little longer reverb decay time. It sounds fantastic.
Give them a try,
Rob
