I was looking at the same kit as i'll be making a decision on a 493 stroker kit in a week or so.....I spoke w/ my machinist/engine builder and he says thats WAY cheaper than what he can get Eagle kits for.
I called mancini racing and inquired why this kit was so cheap and it was explained that the rods are chevy sized (2.20) which brings the price down considerably. Also there is no balance on it (all the better). the only difference that I can see is that the Pistons are Diamond and not SRP like in the Eagle direct kits.

components as stated from the web site:
MANCINI - 493 ci 440 Flattop piston Stroker Kit
Kit includes: Diamond flat top lightweight forged pistons wit .990 pin and Diamond moly piston ring set. Eagle 4340 forged crank with 2.200" rod journal. Eagle ESP H-Beam rods. Clevite Tri metal rod and main bearing set.
$1,450.00
MRE440-493-FLAT

i'm i missing something? it sounds like a craigs list scam. or is this a no brainer, cause the timing couldn't be better.......