The OP is looking to reduce cruising speed, it doesn't matter if it can hit the rev limiter in 5th or not.

Depending on the year of the bike, it's likely either got a 28T or 29T sprocket. Adding a tooth drops your RPM by about 3 1/2%.

So, if you're revving at 3800 RPM at cruising speed, each tooth you add drops your RPM by about 135. ie, if you have a 28T now, and go all the way to a 32, you'll drop it by over 500 RPM. That 32T sprocket gets you pretty close to a 1200 gear ratio.

But you might find an 883 suffers in city driving with that high a gear ratio.

I went through the same thing with my conversion, at 70-75 on the highway I was at about 4 grand. The Sportster motor doesn't mind 4 grand, but I do. Especially after 3 or 4 hours of listening to those pipes. I eventually changed to a 1200 primary and a 30T international sprocket. At 80 MPH now I'm at about 3500 RPM. It's way cheaper and easier just to go with the 32T (unless you have to replace the belt too, I've been told you might not have to though)

 

Stock 883's have always had a higher top speed in forth gear as apposed to fifth gear.
In fifth gear they lack the horsepower to peg the needle @ WOT....... Not my opinion.......Its a fact.

 

Are you sure that's a fact? The chart that HD put out that shows that the top speed in 4th gear at 6200 rpm is 93 mph and in 5th gear at 6200 rpm is 110. And my 883 is a good deal faster in 5th gear than 4th. I opened it up in 5th gear a couple days ago. I didn't get it up to 110, but I came close. Fastest I could get in 4th gear was 91 mph. Not trying to be a jerk, I'm just saying, I don't know if there's factual evidence of that.