I have a 454 (large oval ports 049's and CC 274 solid) with a holley 750, primarily a street car with intentions of strip use in the future. What would be better, the open or 4 hole spacer? Thanks.

On my SB combo, the 4 hole works better on the street. It improved idle quality, and throttle response. Typically, the open spacers help top end with some loss down low. You'll have to try both though, to see what works better for you.

Ah, another one of those "it depends" answers.
What type of manifold are you using?
As was said, it's best to try several different spacers and check the results. Do it at the track if you race, that will give you the best info. But, you have to also re-tune the carb in many cases to get the best results per spacer.
There are more than a few different types and heights of spacers out there. Open 0.5', 1", 1.5' and 2".
4 hole probably in the same increments.
Somethig relatively new are the combination spacers, 4 hole to open often with CNC shaped exits. The HVH super sucker comes to mind.

The problem with trying all of these at the track....besides the cost of having to buy them all....is the time and tuning required vs the changing weather conditions as the day progresses.

Tell the group more about your combo, maybe someone has something very similar and can tell you what worked best for them.

An interesting article just appeared in Hot Rod mag where they tested a bunch of Edelbrock intakes on a BBC, and tried several different spacers on each. Sometimes the combo cared, sometimes it didn't. And it was not only manifold dependant, it was also carb dependant.

One thing that personally I think helps, is the fact that the plastic spacers keep the carb cooler. Significantly I might add.

Ron