Am I correct that electrically one can replace the 95 PWM 3-2 solenoid with a 96- on/off version and run the 95 trans off the 00 ECU?

 

You would need to replace the 3-2 and the PWM along with harness to the 96 up harness. Some may argue but I own a 95 ss impala and have done this with no discernable issue with 3-2 or lockup.
Frank

 

What do you mean by "and the PWM"? 95 has the PWM TCC I've read. Need to ditch the PWM 3-2 for an on/off type but I didn't see any difference between 95/96 for the TCC solenoid.

I also see a lot of harnesses online listed as 93-02, I assumed the harness was the same.

 

OE harnesses are different between 93-94, 95, 96-2002 & 2003-2006 (+ some 2007)
Aftermarket harnesses have an xtra connector to make it universal for 93-2002.
Here's a link to a picture of the Rostra 350-0020 93-2002 harness
https://rostrapowertrain.com/products/350-0020/
I have added their install instructions as well.

 

Ahhh, ok that makes sense. Thanks.

So a 96- harness, a non-PWM 3-2 and I'm good?