I do recommend "rollerizing" between the output shaft & case, This will eliminate the 4-tang thrust washer & 3-tab selective washer & a lot of friction.
You will need.....
TH350 Pump to Direct Drum torrington bearing.
TH350 front end-play shims.
'91-'96 4L80E Pump Bushing.
Measure the thickness of the original Selective & Thrust Washer when stacked together with a caliper, This measurement will be used for 2 purposes....
1. This will give a calculation for the Maximum amount the Case Bushing can protrude above the back of the Case.
2. Starting point for setting Rear unit End-play, Add .010"-.020" to the measurement & start there with the Bearing & Shims. Let's say the original selective & thrust measures .140", Start with the Bearing & Shims at .150" to .160" thick.
A 4L80E Pump Bushing is twice as wide as a TH400 Case Bushing, Giving better support & you can leave it protruding out of the case to center the Bearing, Again let's say your original selective & thrust measured out at .140", Leave the bushing protruding .120"-.130" (.010"-.020" less) to clear the radius on the output shaft & provide adequate lubrication to the bearing.
Set Rear Unit End-Play to .005"-.010", With the bearing.....You can run tighter end-play than factory spec!
The first pic is of the TH350 pump bearing & Shims (TOP), & original TH400 selective & thrust (BOTTOM).
Second is comparing a 4L80E pump bushing to a TH400/4L80E case bushing.
Third is of a 4L80E Pump Bushing installed in place of the original Case Bushing, Shims....Then Bearing.
I was test fitting the bearing to make sure I didn't "Bell" the bushing.....Black side goes DOWN during final assembly!!!!
Forth is checking rear end-play on a 4L80E, Same procedure on a TH400. Set the dial indicator to zero & lift up on the output to check.