If you have stock rockers, they are going to be another limiting factor. Start getting much over the .500 lift point and stamped pieces don't like the increased spring pressures.

More's Law:

If some is good,
More's better, and
Too much is just right.

You seem to be following that to the letter. Back up, pilgrim! Before anyone can make a cam selection there needs to be some information shared. Such as,
Real compression ratio
Rear gear ratio
Converter stall speed, or 4-speed
Intake
Carb
Exhaust
Intended use for the car

Hughes Engines has five camshafts between 220 and 232 intake duration at 50 lift. The 220 cam has 0.503 lift compared to your 0.460 lift. It is possible that that cam would make more power than your cam with the same valve opening and closing points, simply because it gets the valve open quicker, longer.
I know this board loves Racer Brown, but he sold you a Chevy lobe. It does have one advantage, it is easier on the valvetrain because of its lazy lifter acceleration rates.

If you're going for a Comp 274, you get more from the XE275HL. Or comparable Lunati or Hughes cam.

But first what are the answers to the questions above?

R.

http://www.hotrod.com/articles/mopp-0201-cam-velocity-advantage-mopar/
This article is 15 years old. Hughes has an even hotter lobe set now.

For me, the ability to make the same power with a 10 degree smaller cam is very attractive. I like driveability.

Have you answered the questions yet? If not, we're still barking at the moon.

R.

I think with your lack of stall and gear, you might be better off sticking with the cam you have. Going much hotter than what you have risks taking as much from the bottom as it adds to the top. To me, the 274 XE sounds a little big for a 340 with 2500 stall. Now, if you were to put a looser converter in.... Also, some of the high velocity/ high rate of lift cams would make me a little nervous with the stock rockers. Have you had this car on the track? How does it run?

Now that you posted your et/mph, most responses will now be about 60ft times and converter, gear and tires. So, the question to you is: Is it about et for you, or about making more power (i.e. et and mph)?

It is a personal choice. Personally, I prefer making more power. In your case, this would have an end result of 13.2 @ 106 mph, verses 13.2 @ 102 mph, as an example.

So if it is power you seek, I think you are probably going down the right path. I think it might be helpful for the smart cam guys on here to know what your current cranking cylinder pressure is.

Finally, I would recommend a small solid cam, but you will need adjustable rockers. I think there is an undesirable risk with a fast rate hydraulic for you as the valve train seems to start giving it up too early, especially for a small block. And the slower ramp cams will cause a noticeable deterioration of the low speed characteristics of your small block. A solid flat tappet is the best of both worlds.

Are there any decently priced adjustable rockers available if I went with a solid cam?