I personally like the 70 best (like the 73/74, but little differences like parking lights in the top of the front grill.), but to answer your question, to get a better detailed engine comp and chassis, I would get an AMT Challenger. The one you can make either a convertable or hard top. That whole top thing causes it's own issues, but it has a really nice chassis (seperate exhaust & rear axle, not to mention a front suspension with no metal rod.) and front inner fenders that make for a great engine bay. For a really nice SB, I would get an AMT Duster kit. If you can find a street machine version, it has some really nice MP valve covers.
Keep us posted.