Electronic to Mechanical Speedo Conversion

[81Cheyenne]

I'm changing out trannys from a 350c to a 700R4.  The 700R4 that I'm putting in is set up for an electronic speedo and looks like it has a purple drive gear.  My mechanic has found a mechanical drive housing.  I'm putting in a 3.73 rear end and will be running 29" (235/75-15) tires.  What size driven gear will I need?

[joesgarage71]

 This might help
http://www.2quicknovas.com/tranny.html

Or there is some good info here.
http://www.csgnetwork.com/automotiveconverters.html

[Captkaos]

here is another one:
http://www.73-87.com/7387garage/drivetrain/speedo.htm

[81Cheyenne]

here is another one:
http://www.73-87.com/7387garage/drivetrain/speedo.htm

Yep. I saw that. But did the later model 700R4's with the electronic speedo setup have a different color drive gear?  I haven't had a chance to go over to the garage to see it but my buddy said that it looked purple. 

[Captkaos]

should use the same.