The people at your local UMASS Cooperative Extension Service office would be better able to answer that question because it will vary depending on which plant you are working with.
Understand that changing the soils pH is going to take some months and is not something that will happen shortly.

The pH is fine for most plants. You may find some 'mysterious' failures, but I wouldn't worry about it. The lawn will be fine, and so will most of the perennials.

The acid lovers, of course, are a different matter. Whatever you do, you may lose them, but adding sulfur is a start. You'll want to do another test next spring just to see what is going on.

Do you know of any local places with lime in their name? There are around here, and Soil & Water tells me that the natural pH can be as high as 8 locally.

Thanks for the tips. Our local soil is usually in range 6-7. All of this soil was brought in earlier this spring...not sure from where but probably nearby New England.

I realize it will take a long time for the sulfur to work, and not much will happen during the cold months, but was wondering if I should get the process underway now or wait until Spring to see if the 53 ppm S currently in the soil will acidify it.

I'll check with umass too.

"wait until Spring to see if the 53 ppm S currently in the soil will acidify it. "

No, it won't. That sulfur is in the form of a neutral sulfate salt, probably calcium or magnesium sulfate. Sulfur has to be in the form of elemental sulfur or an acidic sulfate salt (iron sulfate, ammonium sulfate, aluminium sulfate) to have an acidifying effect, with elemental sulfur giving you the most bang for your buck.

Since 7.5 is close to the acceptable range, and because the surrounding soil is acidic, I would try to lower the pH using ammonium sulfate and organic sources of nitrogen. With elemental sulfur, there is always the risk of overshooting your target.

OK, again thanks and sounds like good advice. I thought it might be useful to post a screenshot of the test results. Does anything stand out to you experts?

Is the soil just topsoil or is it some kind of garden mix with compost or manure mixed in? If it's a mix it may have had alkaline manure mixed in. In which case it will not stay up there permanently. Just a thought. I don't have much to add to what's been said already.

Also a factor ... how do the plants look?

If they are sending out now growth and in general looking "happy" I'd leave it and see what happens.

If they are not increasing in size, yellowing, dropping leaves and doing the unhappy plant stuff ... see about lowering the pH.

It is a "planting soil" and is supposed to contain compost and I think it does given the test results including near 6% organic content. My inclination is to go slow and watch what's happening.

The plants are generally happy keeping in mind that everything (60 trees and similar number of shrubs plus hundreds of perennials) was just planted this spring. There's some transplant shock and we have lost a few trees and shrubs but overall they look pretty good. We have had a very dry (for NE) cool summer.

Surprising to me the blueberries all look great. Their leaves look good, starting to turn normal red. The azaleas are also mostly happy.

The perennials were looking nitrogen starved and i have now fertilized them. On the advice of an arborist I'm not adding any fertilizer this year to the trees as they settle in.