Technical 1950 shoebox speedometer issue

Ok,, I bought a shoebox with a chevy 350 already installed..The person told me it had a TH400 ******..no problem..i am in the process of rewiring it...I jacked up the drivers side to measure for a new speedo cable going to my stock speedo and,, no input..Looking closer all I can see is a Plug where the speedo cable should go!! looking closer and searching online it appears I have a 700r4 ******! Now...how can I adapt (if possible)my stock mechanical speedo to this Plug thingy on the ******??? if at all

 

Answer will depend on which ****** you really have. If you are not sure, you can tell by the ****** pan. You should be able to find comparative diagrams of the pans on HAMB or google it.

 

pretty sure its a 700r4..theres also 2 wires in a connector by the shifter linkage which im ***uming is for the lock up mechanism.