Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

Could always explain to the customer the pros/cons of the items in the build, make a recommendation(s), and proceed with the build. If the customer ends up not happy, he can pay you to do it again, but perhaps he'll have more of an "ear" the 2nd time around. :)
Money talks, and mine speaks the loudest when it's leaving my wallet :D