All the 4L60e have a 3-2 solenoid. You posted on-off so I believe you mean pwm vs on-off. I have read maybe it changed from PWM to on-off and then I have also read that it just changed in design and resistance. I don't know which to believe, but it seems to have been PWM controlled. I've looked before and never found anything that actually verifies the operation for certain.

I am using a 96 transmission behind a 95 LT1 and it works fine. I can't say if the 3-2 solenoid actually works or just being connected is enough it doesn't set a code. From what I understand, the 3-2 solenoid only changes the firmness of the downshift. On = softer downshift and Off = firmer downshift. So, on the older ones if they are PWM then they will vary between on and off instead of only being one or the other. If the 95 PWM doesn't provide enough power to the solenoid to move the valve then I the 3-2 valve would just be off and the transmission would have the firmer downshift. Eventually, at low throttle the PWM level should get high enough that the solenoid will move the valve on. If it did that, it'd get the required on-off operation anyways.

Apparently, you can block the 3-2 valve and the transmission will still work right. Some builders and shift kits do that. So, it doesn't seem that important.

If you can find a table in the tune that gives the PWM output curve then set it to 100% for low throttle and 0% for high throttle. That would make it on-off control. I haven't found a table like that in the LT1 tune so I didn't do anything with it.

I do believe you can swap your 95 valve body into it if you needed to. The 3-2 solenoid is a difference resistance and the computer might not like it and throw a code. You can't just swap the solenoid, the VB is also different where the valve mounts.

Overall, you could try it first before changing anything and swap a 95 valve body onto it if it doesn't work. Of course, if you don't want to do the swap under the car then do the VB swap first and be safe.