Clutches and steels will NOT affect end play. But you do measure those separately to make sure you have the right clutch clearance. I usually eyeball those. If you put the same amount in, unless you making a change for a reason, like for a Z pack or Commercail Alto Pack in a 3/4 pack for the 700r4, then you follow their recommendations in that scenario.
The only selective thrust washers I'm aware of, is the one at the back of the case on a Th400, and the the shims on the front pump of a Th350. You measure the end play on the front input shaft. Push the input shaft in as far as you can, then measure with a dial indicator how much you can pull it out. OR push the shaft in as far as you can. Clamp a Vise Grip onto the input shaft up tight as you can get it to the pump shaft. Then pull the input shaft out as far as you can, then measure the distance between the Vise Grip and the pump shaft with a feeler gauge. That will tell you what your end play is. I also rarely measure that. I can usually tell if it's right by pushing it in and out. The big reason you want to check end play is for #1 to make sure you didn't leave out any thrust washers and #2, to make sure you assembled it right and got all the clutches clocked right and fitting the ring and sun gears properly. If there's no end play then the input shaft probably won't turn at all cuz you'd have it all bound up when you tightened the pump. If you're sure you've got it together right, I'm about 99% sure you've got it right. I don't recall ever having an end play problem when I used the right parts and I've also interchanged drums and thrust washers types, and from thrust washers to torrington bearings etc.
