In the days of yore we used to run engines on the garage floor, chained of
course, to prove to the customers  the engine would run.  You should be able
to run your carbureted engine in the car.  Support the rear of the engine,
otherwise you might break a motor mount and I would remove the torque
converter or clutch/pressure plate to avoid surprises.

You should be able to punch the studs out with the axle on the car, make a
sleeve and a lugnut to pull the new studs into the axle.

Bill

67 coupe --  sure start the engine without a tranny -- just make sure
the back of the engine is supported well -- Very well --  I used to
get 2 jack stands take abar or 2x4 across back of engine with jack
stands on each side to support it  then crank . As for ur studs safest
way is to pull the axles- since its 67 - u should have bearings redone
anyway -- have studs pressed out and new pressed in-- just loosen the
4 bolts to back plate put drum on in reverse- put lug nuts back on and
quickly pull the drum towards u it should be enough that u see the
axle plate move out -- this way will also make sure that u dont use
the standard axle puller which people seem to use to hard and pull the
axle so far out so quickly that after it exits the housing it falls to
to the ground and damages the splines (gears) at the end