They are suggesting incorporating sulfur to lower the ph of the soil. The sulfur will become sulfuric acid in the presence of water. If the soil had a ph of over 8 or you were a commercial farmer this would be a viable solution but would have to be done yearly.
Your soil ph of 7.4 is not extremely alkaline. Although most vegetables prefer a ph of 5.5 to 6.5 these vegetables will do well in your soil:
- brussel sprouts
Refer to this pdf which has a detailed list of what likes what. You will see that with your soil ph these vegetables will not do as well:
Your best investment which would help your garden in many ways and moderate your soil ph would be to add organic matter.
To grow the vegetables that like a lower ph you could consider a raised bed with large quantities of composted manure mixed with top soil. In my area they have a "triple mix" of composted manure, top soil and peat moss. If you have six to eight inches of a soil high in organic matter and you top dress it every spring with more organic matter then you will not need to use sulfer.
Edit: Yes, I am suggesting that you would be better off with a raised bed of your favourite mix of compost and top soil and grow the ph sensitive vegetables there. Skip the sulfur...