The Magnavibe was inspired by the early 1960's vibrato guitar effect (not the typical tremolo which is just pulse modulation). The Magnatone amp was known for having that amazing wobbly sound. Setting out to put that type of sound in a box and use it with any amp took much experimenting. The results are excellent. This is not a plain one dimensional vibrato such as a chorus pedal with the dry mix removed. Delay chips weren't even used back then. Nor is it just another uni-vibe clone, but a unique sound with that classic unique tone. Adding spring reverb or delay after the vibrato sounds especially good.
I've drawn it so there's space to use a VTL5 or similar photocell, or you can make your own. Either way, theres space for it. A lot of layouts I've seen don't allow for a comfortable enough space to get the LDR and LED lined up nicely. You might even be able to get this to fit in a 1590a.