A 540 will make a ton of low end power, but I still think you need to consider your compression when choosing a cam. As I understand, with lower compression, once you get to a certain point, bigger cams start to kill low end power and dont add a whole lot to the top end. I would try to find a cam that matches the powerband of the heads. Those heads are recommended for under 7000 RPM and under 500 cid. Being that they are going on a 540, that just means that the RPM range at which they will make power will be reduced. I figure they will run out of steam around 6000-6500 RPM on a 540. I assume you will be around 10:1 compression. Being that it says under 7000 RPM, I think a cam recommended for a 3000-7000 RPM range would be about as large as I would go. That will also test the limits of your compression. As an example, the 306S cam by comp is 260 @.050 .629 lift recommended for 3000-7000 RPM, but it is also recommended with 11:1+ compression. The 294S is 248 248 @.050 .595 .595 lift, recommended for 2500-6500 RPM, and with 10:1+ compression. I think something inbetween these two would be your best bet. For instance, the XS290S (252 260 @.050 .598 .598)may not be a bad choice it is recommended for 2800-7200 RPM, but they dont give a compression recommendation. You can go larger, but I think you will just be creating a miss match for where your heads are going to want to make power, and the amount of compression you will have. You may add a little on the top end with a bigger cam, but I bet you will really start to widdle away at the low end power. Any one else have any opinions or experience with respect to this? My guess is that you will be in the 625-650 range wtih a cam like this at around 6000 RPM.