It is now time to get the transmission dust cover and starter ready.

The starter used here is Ford-built for some of the bigger Ford engines
It is also known as the JEEP starter. Ford built them for AMC V8
Made for the V8 Jeep from 1966 into the 90's
I usually tell the parts store I have a 1976 Cherokee with
a 401 or a CJ7 with a 304 engine.

Remove the small "can"  from the side of the starter.
Drill a small hole (1/16 or 1/8) in the can to prevent moisture from
accumulating in the can later on.
Just for now leave the "can" off of the starter.
Temporarily bolt the starter in place on the engine plate.

Do not spin the steering wheel until after you have carefully
 determined that the steering arm will not rub the starter
or hit any terminal that is too long or damage anything.
Some makes of cars including Chrysler and Studebaker
would mount their engines offset to the passenger side of
the car.

More often than not, people will put their engine back in
and try to center it in the engine compartment.
I have seen STOCK Studes with STOCK starters have steering
 arms that rubbed the starters. You will need to make sure that you
have steering clearance. You may have to move the engine over
to where it belongs if someone centered it earlier.

Check the operation of the starter and check for gear mesh.

You can activate the starter gear to see how it fits the ring gear
by pushing on the magnet-lever that was covered by the "can".
It is not likely to need adjustment, but if you want to increase the
clearance in the gear mesh, you can grind or file the side of the large
starter hole to allow you to  move the starter away from the ring gear slightly.

Now is the time to rotate the engine a turn or two to make sure
 the ring gear clears everything inside the bellhousing.
The GM flexplate is just what the name says- it's made to flex to
accommodate differences in different parts. If it has been bumped
or pushed and has some runout, it is perfectly acceptable to
push it forward or rearward to get it to run straight again.
When the starter and ring gear are ready, remove the starter
install the dust shield (I usually run without one) and mark where you
think you will need to trim the shield for the starter.
On my pickup I used tin snips to cut a "V" shape in the side of
the dust shield to match the shape of the starter snout.

After my starter was bolted in place, I ran a bead of caulk
(optional) around the edge of the hole to make a nice
clean-looking installation.
So far I have been driving it for over 9 years on this starter,
but I'm sure that when I need to replace it, the starter can be
unbolted and pulled away from the silicone caulking
without too much effort.

Raise the rear of the transmission to it's intended ride height.
Usually that is as high as possible without the driveshaft rubbing
the floor when under a heavy load. The first and simplest cross member
we made (LARK race car and my pickup) was a piece of channel iron
 bolted across the underside of the frame rails in line with the stock
Chevy rear tailshaft mount.

We used a 5/8 or 3/4 inch spacer under the Chevy rubber mount.
On my pickup where there was a crossmember running very close
under the flywheel. The engine and trans had to positioned very
 carefully. Everything worked well for the first few years.
Eventually the inevitable rubber mount sag set in.
One day I heard the flywheel gear lightly touching something.
I raised the trans with a new rubber mount and it cleared up.
A few years later- same thing.
I then used a urethane trans mount for Chevy (AutoZone) and it
never sagged again. I think it was only $10-20

IMPORTANT!
I guess this is the best place to insert this info-
Although we never had this problem with the race car,
I have been told by one Lark owner that he had better
bellhousing clearance over the Stude crossmember (the
one that runs from doorpost to doorpost and under the frame)
 by dropping it down and then bolting it back in place with
washers or spacers between the frame and crossmember .
I think he lowered it about 3/4 inch for the flywheel dust cover.

My Hawk never had that problem. It only happens when the
clearances are so tight that you don't have room for a bit
of sag in the rubber. Urethane mounts are my favorites now.

Slip the proper yoke into the back of the transmission, then pull it
back out a little bit (1/2 to 3/4 inch?).  Follow the standard procedures to
determine the new driveshaft length, carefully measuring from yoke to yoke
using the center of the u-joint as the measuring point.
Measure when the car is at it's usual ride height,
 measure when it is
riding low with a load in it,
 and measure when it is up high on a jack.
Make absolutely sure that the yoke doesn't bottom out, and that
it doesn't slide out so far it may leak, wobble, or come out.

I usually sort thru the driveshaft pile at the local junkyard.
Many people have the local driveshaft shop make one.
If you don't have one nearby, sometimes a big truck repair shop that often
has the need for driveshafts will either tell you where they do business,
or will have the machines of their own.