Technical 3sp trans and a over drive .. whassit ?

Depends on which one it is. The OD unit was used behind all sorts of transmissions, very few of them could be considered as a performance piece. The one exception is the T85/R11 version. This combo was very nearly as tough as the T10 (or maybe it's equal at the time). Ford thought enough of it to install it behind the 360HP 352 and even the 401HP 390 before the T10 became available early in '61. They also offered it behind the 428 in pickups until the early '70s. I would expect a good used unit to fetch a premium price because of that along with their rarity.

 

The other way the light duty might be worth something is the low production cars. Some versions were in Studebaker’s etc. but you’d have to find just the right buyer. Pretty thin market.

But with the usage “6 cyl” and “cruiser” it’s a fine upgrade for the OP.

 

I can't see the flat blade terminals good enough to figure out the orientation but here is a rear brake/tail light wiring connector plug for a 67-72 Chevy truck....

 

Just saw this on FB.

https://www.facebook.com/share/1GwmzV4Tsy/?mibextid=wwXIfr