rally kits???

do all rally kits have the chassis detail molded in or r they separat parts??

It depends on which brand of kit that you are getting.
tamiya is seperate.

Tamiya kits (1/24) have full underbody detail - drivetrain, exhaust, suspension etc.
Hasegawa kits (1/24) have some of the drivetrain and exhaust molded into the chasis, but full suspension etc.
Heller/Airfix (1/24 & 1/43) have none of the above, with exhaust and drivetrain moulded into the chassis, and no suspension at all.
None of the above kits (except for older Tamiya kits) have detailed engine parts.

Don't one or two of the Hasegawa kits have full engine detail? Lancia 037?

Correct, the 037 rally has full engine detail, but you can only see it through the window... still, it's a nice model:)

Hasegawa WRC kit are better than Tamiya kit.. they also have lot more of piece (Corolla 160s part vs 65 parts i think)

True, but I think the Tamiya rally cars are more accurate then the Hasegawa's. Compare Lancers with each other and you know what I mean. ;)

I agree about Corolla, but all others Tamiya kits are better.