just picket up a older c-dale bike its 6speed friction suntour i have shimano 600 dt shifters that are friction/sis can i swap these out???to get sis shifting?? thanks scott

Yes, but you'll have to change the derailleurs too...at least the rear.

but I think the whole index shifting started up again with 7 speed, the spacing won't be index correct and shifting might not be correct. You could try and see if you can make it work.

I think you will also need a 7sp uniglide rear cluster. And maybe a chain. 6sp has different spacing.

The mod you are talking about is exactly what I did in 1986. I kept the Suntour ratchet front shifter though, as it was much better than the Shimano 600 friction shifter.

but I think the whole index shifting started up again with 7 speed, the spacing won't be index correct and shifting might not be correct. You could try and see if you can make it work.

She doesn't ride much, so she still has bikes from the mid-'80s. Her Bridgestone MB-3 came as a five-speed friction shifter, but I bought parts at a swap to convert it to a six-speed clicker. Straight freewheel-and-shifter changeover, no issues at all. Her roadie came from Bstone w/indexing and still works fine, though she's probably approaching, oh, maybe 1500 miles total since new.
The parts are out there, if you want to do it. At least for me, though, it wouldn't be worth the trouble. Two of my four bikes are still friction, and I go back and forth from index to fric with no adjustment period at all. If I could change them all to SIS for a buck, I wouldn't spend the time or money.