I use a 9a gear set with a welded diff and 3.9 final.
You should have less than 700rpm drop into high gear. The 5 speed is leagal isnt it?? If you run sebring, daytona and Roebling the 3.9 is pretty nice with a small 13" tire, some run a 4.2 but I cant see why.
The guy that does my trans is just north of tampa, Jim Loftin, does very nice work for fair price. He is in the CFR monthly adds. I can get his # if you need it tues or call my shop. 352/796/1985 after 10:00
I have a 16V trans to build but it has a 3.67 and not for a 1600 race setup. I may also have a welded 3.9 in the box .
Bill. I was using the 7k as a reference, not a suggested shift point. I shift my 1.8 at about 6300 3-4 and 6200 4-5. But many 1.6 racers run them well up near 7k, all the time, with the G cam late timed.
IMHO MM