This is a VERY popular topic. Here is a cut and paste of a response I made on another board just last week:
Debunking some other 351c myths you will hear (not here) but out in the world when you talk to people.
2v vs 4v
The 2v heads are 'historically' known for better performance in street applications. The most common statement I hear is "4v heads and a 351c will have no low end"
While the above statement is partially true it is very misleading, many people who know little about the 351c latch onto this statement and like to hammer Cleveland fans with it.
A better statement would be that 4v heads produce a smaller % of their total power at lower RPMs than their 2v brothers. That is not to say they do not produce good off the line performance, but as a function of their total performance they perform much better at higher RPMs.
If you are looking to build a 351c and have 4v heads, you can really have a lot fun by stroking. While the 351w crew HAS to buy new heads when they build a stroker, the C runs great with the stock heads. As stated previously, you just upgrade the valves to one piece and you are done. You don’t have to port or polish (you can if you want) and the 4v heads will support the flow requirement of your now larger cubic inch motor.
I can use my own build as an example, with what I would call a mild hydro cam (.5885 intake/.5887 exhaust) and a 408 stroker setup I was able to make 395 RWHP through an AOD (10 inch 3k stall) and 9 inch rear.
Cheaper to build a Windsor
One of the most common arguments you will hear about building a 351w over a 351c is not necessarily parts availability but parts costs. Items like intakes, pistons, crank, etc tend to cost a couple dollars more than a corresponding W piece (take my oil pan for example…it was $25 more than the W part IIRC). As a general rule though, I always say to build what you own. If you have a 351w and you want to build it up, after you pay for heads the total price will be right around the same if you built up a 351c (since you didn’t have to buy heads). To state it another way, if you factor in cost to source blocks and other incenditals to build one when you already own the other, it will end up costing more (in general) to meet the same power numbers as if you had simply built on the platform you already had.
The Aftermarket is much better for a 351w
Also not true, there is an abundance of top-notch parts coming from OZ and most are readily available in the US these days (read full thread here:
http://corner-carvers.com/forums/showthread.php?s=&threadid=9186). I prefer to look at total performance potential than get muddled up looking for red herrings from both sides of the camp as to which motor will perform better if we do this or that. I like to boil down the comparison as follows (perhaps an oversimplification but it works for me):
Stock 351c vs Stock 351w – 351c wins
Stock 351c vs Mild 351w - hard to call
Mild 351c vs Mild 351w - 351c wins
Mild 351c vs Mod 351w – 351w wins
Mod 351c vs Mod 351w – the one who spent the most wins (or more precisely, the one who spend the most time researching and understanding how certain parts will interact with each other and developed an action plan to assembly a motor with a clear goal in mind will win)