The Spectrum 44 ton and 70 ton diesels do not have 8 pin connectors. Just solder tabs like the steam switchers mentioned.
If you ever get a non Bachmann loco, below are some connector options.
The Specialty one is quite new and selling well from what I have heard in a DCC forum.
http://www.litchfieldstation.com/xcart/home.php?cat=255Rich