I have 1967 F100 4x2 with a 300 I-6 & NP435 transmission. I want to put an overdrive transmission in it. What manual overdrive trans will fit in its place with little to no modification?

 

You left out the part about what engine are we talking about here?

 

Also 2wd/4wd? A OD will not be cheap. Do you use your 67 as a truck or more like a car? Want a low first geared trans or a car trans like a TKO with a high first gear? For an FE engine, there are several options like a NV-4500, A Bendtsen's adapter to mate a SBF trans to an FE, and a Gear Vendors OD. If a 240/300, then these use a Small Block Ford bell housing which you can use any SBF trans like the M-5OD and the ZF-5.

 

I would look for an M5OD-R2 out of a late 80s early 90s bronco/ or F150.

 

A T5z...........

 

M5R2 5-Speed Transmission Swap Into 67-72 F100 - FORDification.com

 

If you go with the M5R2 look for one that is a '91 or older. '92 and newer are not drilled for the cable driven speedometer our trucks use.

 

Tremec T-170/"TOD"/RTS is a direct replacement 4 speed OD trans. Mid 80's models. Move the shifter hole back about an inch. Uses a C4 type slip yoke. 2-3 gear spacing is very long, but liveable with enough torque.