Ok, so i voted for C....
I say find the BEST chassis that you can find, and start there first... Then, you can pull the motor, and one step at a time, clean it up... sell the stock motor that came in it, and use that $$ towards the B. Then, let the car sit there, and clean parts and pieces of it a little bit at a time, and maybe do some minor upgrades on it over the winter while you build the motor. Then, in the spring, finalize the motor, and then the car will be 100% done and ready for the motor to be installed into it.
This is the path i'd go down in your position.
If you buy the motor first, you may not have the $$ if a PERFECT crx comes your way... the chassis is WAY WAY WAY more important than the motor... you can ALWAYS find good clean parts for motors, but you can't for the chassis.
Don't do option B, whatever you do.... all this will give you is a POS that you'll spend WAY more time and $$ on than if you had just spent more on a good one to begin with. How muhc is your time worth to you? Factor that itno the equation when you are figuring out how much work a car will need when you buy it.... sure, you're saving money initially, but you'll spend more time on it than its worth in many cases.
Chassis first, buy the best you can no matter what... don't settle. then the motor 8)