What kind of rockers???

What kind of heads are on the car?

Stud mounts are supposed to be the best.
The diameter depends on the size of the studs in the heads.

There are actually a few things to consider.

The milage and condition of your valve springs. If the are old and worn, adding 1.7's could increase your chances of valve float and even coil bind. Additionally, adding 1.7's often requires clearancing the valve covers by removing the baffle and maybe grinding down some of the inner bracing. You will have to test fit them to find out.

Your stock rockers are 1.6 ratio and are pedistal style.

You could stick with a pedistal style or do like I did and go with the Crane stud conversion kit which will allow you to use stud rockers without having to remove your heads and have the machined for studs.

If you have a low milage motor I would consider 1.7's . If you have a high milage engine I would stick with the 1.6's for now.

I went with the Comp CAM stud mount conversion and 1.60 steel roller rockers.

FMS 1.6 full rollers with pedestal mount.

Enjoy
Unstable Performance