hard engine starting

10.6 v is in the spec range for startup for the MSD so that seems OK. And starter circuit seems fine since speed is good. So it sounds like fule/air mix or spark is not right.

What 67dart273 is saying is to first check spark right out of the MSD coil wire first to make sure it is good from the coil. I would disconnect the wire from the coil from the distributor and set the distributor end of that wire about 3/8" from metal. Crank for a second and watch to see if a hot blue spark comes out the first crank when cold. Then reconnect that wire to the distributor, pull a plug wire from its plug, and put the open end 3/8" from metal and again crank, looking for a hot blue spark. If good both times, then you know spark is good and the fuel is the issue.

If the spark is good, I would pour about 1/2 teaspoon of fuel direct down the carb and crank. If things are right in the spark, then it will fire almost immediately and run on that small gob of fuel for a second or so.
As above, any choke in the carb?

What temperature is it there now?