A lot would depend on which one it is ... there are a few different twin damper kits around ...
Has to be said, thobut, if you're going this far, perhaps you ought to be able to figure it out yourself ... twin dampers are for when it gets really serious, and aren't meant to simply bolt on, and be made to work in ten minutes. OK, so some maybe people could, but asking for instructions doesn't bode well for such bits of kit. There's a lot more to this type of conversion than simply bolting/welding stuff together.
What project is it? Be interested to see any pics you have, or any plans you might have made for what it's eventually going to be.