I've been involved with the 302 vs 351 discussion 2-3 times in the last few months and what it all boils down to is what you want to do with the car in the end. If you want an all out street - strip car, then for sure you want to go the 351W route. The 302 is about done with cubic inches somewhere in the 347 range while the 351 will go to 427 and more. There are a couple of areas that might cause you concern in your Comet - spring towers if you still are using that suspension. The 351 is an inche plus taller and two wider at the top then the 302. These are close - http://www.mustangsandmore.com/ubb/E...imensions.html.

Then of course, the cost - a 351W based engine is significantly more expensive - 15 to 25% more, something like a SB Chevy vs a BB Chevy.

The engine in my current car is based on a 302 crate motor with many additions. It was relatively inexpensive. My last car had a 351W .030 out to 355 and was a high end used engine build - and cost a fair amount more then my 302W. Given the chance today and knowing what I could have put in my car now, which was an unknown, for sure would have stepped up to the 351W.

And the C4 - never had a problem with either car. The C6 is a great transmission - but big, heavy and fairly expensive. A possible better choice with gas continually getting more expensive might be an AOD - and with them, there are "good" ones and "not so good ones" and that's the limit of my knowledge of AOD's.