Different size torque converter knob 170 vs 225?!? Are you kidding me?

The difference isn't 170 vs. 225, it's that the torque converter nose and crankshaft counterbore were enlarged for the '68 model year.

You cannot put a '67-down torque converter (with small nose) in a '68-up transmission; you'd also have to change the input shaft and some other parts.

Sounds like the 170 you want to put in is in fact a '60-'67 engine (or at least has a '60-'67 crankshaft).