I could be wrong but as far as I know you need to apply the clear coat as part of the two pack system. Its the clear that gives the color the shine, depth and protection. Without it the color is pretty ordinary and would fade pretty quick i think.
As for using todays acrylic to match yesterdays factory finish it cant be done so easy. The factory baked the primer then according to my manual applied an acrylic resin base enamel also baked. the result of this was a hard glossy finish which in my opinion more resembled todays two pak than todays acrylic does.
There are pros and cons to applying both finishes but as far as Im concerned two pak is way superior.
If a concourse competition car is your aim then you have a problem to solve but for the rest of us its two pak all the way.
Matty I want to see that car shine