my 68 300 vert rear power window move very slow. how hard are the motors to replace? are they the same as the front motors?

They will be the same, theres a right & a left...But...Most of the time the problems are something else..Old grease especially during colder climate operation....& the biggie reduced power getting to the motor due to resistance in the switch, connections & wiring...I'd start with pulling the door panels & try lubing them...Then with a fully charged battery try hooking up power directly from the battery to the motor, two wires, reversing polarity reverses motor rotation...If it runs good at that point changing the motor would be a waste of time & money..

If you care to spend the time adding relays is the best fix...
https://board.moparts.org/ubbthreads/show...&PHPSESSID=

Might want to try " c-body dry dock " too.
These guys are into the big cars and do a lot more with luxo type options.

The rear qtr windows are a bit of a pain to get out.
The regulators have to be pulled and clamped before you pull the motor.
There is a spring in their that helps them move and it is loaded.

Most times if it has always been slow, someone took it apart and did not put the spring back in.

Most people cut part of the inner metal so they can get them out, but it is not necessary.
I have taken both out of 2 different c-bodies and did not have to cut anything. But it sure would have been easier.

I think the motors in the newer cars like the 80's newyorker m-bodies are the same, but the connections are different, but I am not positive on that.
I do know there are several places to have them rebuilt fairly cheaply.
Usually though for the rear ones, the problem isn't grease or bad connections, it is rust.

The verts drain all the water through a hole just under those motors. Both cars I took apart had rust on the motors. Even the replaced set was starting to rust.