Hopefully I can explain this well enough to help you out. Based on what you have told me, I would recommend a cam in the neighborhood of 270-274* of advertised duration. But your question of which lobe center to use, is a good one, and asked often.
The 274 is an excellent street cam and an excellent choice for your application. The power curve of this cam is approximately 3500 RPM. In other words, it will give the best performance within a range of 3500 RPM.
The lobe center controls where the power curve is applied. This cam with a 112* lobe center will come on around 3500 RPM (not to be confused with the power curve - which happens to be the same RPM). Changing the lobe center to 110* will lower the point where the cam starts working (kicks in) to about 3000 RPM. And changing it to 108* will lower it to approximately 2500 RPM.
Therefore, this cam with a 112* lobe center will perform best from 3500 RPM to 7000 RPM. Most of our sixes will never see 7000 RPM, so in my opinion it is too much. The same cam with a 110* lobe center, will perform best from 3000 RPM to 6500 RPM, which is where most prefer. The cam with a 108* lobe center, will perform best from 2500 RPM to 6000 RPM, which is great for a street/track motor where low end power is desired.
But keep in mind, a cam with a 112 lobe center will idle better than one with a 110* lobe center. And a 110* better than one with 108* lobe centers. A 112* will give a smooth idle, 110* will be a bit lopey, and 108* will be choppy. The 108* cam is fine with a manual tranny, but an automatic may require a matched stall converter (2400-2500 RPM stall) for ultimate performance.
Inches of vacuum may also be of concern if you have vacuum assisted accessories, such as power bakes. This cam with a 112* lobe center will pull 16-20" of vacuum (good for power brakes). With a 110* approximately 14-18" of vacuum (still OK for power brakes), and with 108* about 12-16" (which may be borderline for power assisted accessories). This can vary a few inches one way or another, depending on other factors, and your individual engine specs. But this will give you some idea of the manifold vacuum they pull, which needs to be considered if using power assist accessories.
You just need to decide which will work best for your application. If you want a smooth idle and do highway driving where passing power is of concern, the 112* might be best. If you do a lot of light-to-light driving, and like a lopey idle, the 110* would be better. But if you want to eat V8's off the line, and don’t mind a choppy idle, the 108* is far better suited. Basically, it comes down to a compromise between performance and idle quality, base on your specific driving requirements.
You asked about a cam with a 114* lobe center, which I would not recommend. It would put the power curve high up in an RPM range where you would minimize the benefits of installing such a cam.
I hope this was clear and assist you in choosing the right lobe center for your application.
A last word of advise. Once you get your cam and are ready to install it, be sure to pick up a Cam Degree Kit and degree the cam to the manufacturers specs when installing. Many manufacturers suggest installing the cam three or four degrees advanced. This also lowers the power curve of the cam and increases low-end torque. At the same time, it sacrifices top end power, but more is gained on the bottom end, than is lost on the top end. It should also be noted that some manufacturers, such as Comp Cams, grind their cams with a 4-degree advance automatically included. So you need to verify this prior to degreeing the cam. All Clay Smith Cams (FSPP's supplier) are ground straight up with no advance.
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