I realize there is always more than one way to skin a cat. I'm not suggesting others do it my way and having done it the same way for 50 years I'm not likely to change. A little tape some oil and close attention as it goes. I have five engines in different stages of assembly now. I have changed clutches in the car and the bolt does work just not my cup of tea. Steve (CTR) 

Don't forget that later cars have bolts for the transfer housing not studs.  It may be possible to do without studs.

Installing the primary gear oil seal before assembly is asking to damage the lip.  The best way is to install it after trial fitting and shimming the primary gear to the crank.
Lube the seal and the applicator tool, slide the seal up the tool and over the splines of the primary gear onto the seal face.  Fit the primary gear onto the crank and engage it with the drop gear.  The seal installing tool is designed to be wound into position using the crank bolt - it doesn't need to be hit or pressed, just bolted into position.

One tooth give you half a final drive ratio, for some that's worth it.

Yes, we do get off topic kind of. As it turns out I now have three sets of the kit to remove primary. Which includes the seal installer. I use one at the press to install seal in housing before installing housing. 

The state of this board is such there are few who will offer advice. And there are a few who offer thoughts on everything right or wrong. I don't think adding a single tooth to primary gives enough change to justify the effort. Steve (CTR) 

I tried once to replace the Transfer case housing gasket In Car.

 Remove clutch + FLywheel
    Removed all  housing bolts..   With nearly everything else still connected the housing would not come away far enough off of the trans studs.. and would also run into the subframe .   Side cranking the engine put too much stress on exhaust + radiator and such.

 Wasted effort,  Ended up pulling complete lump Much easier = re assembly out of car.
 
If you really wanted to extract the trans case studs= you could but what a continual pain.

Undoubtedly the original question was about the CWP - a resounding no from the crowd.

As is often the way though, we've all digressed into a different discussion and learnted sum stuff...

Do ing a clutch/primary gear in situ isn't great, but is a whole heap easier with the proper tooling.

OK if you say so, I have done clutch and seal in the car and did not like the working position. I guess if only changing primary it would be fine. I was thinking of the first motion input gear. Not thinking of the simple way. Wonder if the question was about changing the CWP? Steve (CTR)

You can easily change the primary gear for an economy one with the engine in the car - no more difficult than changing the oil seal or a clutch.

Allow me to rephrase the question. Have you changed drop gears in a complete with inner fenders car? Steve (CTR)

Run a 23 tooth SC input gear, then you can swap primary gears, 24 tooth for a lower final drive, 23 for a 1-1 or 22 for a higher final drive. No inner panel on race car makes easy work to pull clutch and change. 

Can I ask if you have changed drop gears in the car? Steve (CTR)

Or yes, by changing the drop gears. But you still have to pull the clutch in the car. Easier to remove power unit.

In a word No.  To change the crown wheel you need to remove the differential cover, take out the differential, remove the diff bearing and the six bolts holding the crown wheel to the differential - and while you're in there you look at the diff pin, spider gears, bushes, etc. to see if they need to be replaced.  Then there's the pinion to change.

Can you make the change without pulling the engine and transmission?