They are tight, you have to get a special starter if you're running a 727 or a 10.5 clutch. and once they are in you have to leave the motor mount loose so you can riggle the motor a round to clear the torsion bars. I'm running factory A body big block bars in a 65 Cuda with a 4 sp so you have to monkey a round with the fork to stop it from rubbing the headers. Overall I'd use them again though.
And I'd say it's only a 6 out of 10 in the hard department. If you can mini tub or move the springs in it's not to bad of a job. But considering how much you pay, yes they should have better fitment.