I've heard that you should align the rear edge of the doors to the rear clip first and then adjust the front clip so it matches the front edge of the doors. Seems like you've need to have the doors on to get it set just right.
I'm going to be doing this same project sometime this year, so I'd love it if you took lots of pics and some notes!
I have a new Ecklers 80' front end that I was going to put on a vette I had, but I ended up selling it without the front end installed, so I didn't get a chance to do it. I think I have installation instructions somewhere for it. If I find them, I'll PM you.
BTW, anybody want to buy a new 80-82 front end for a great price and that could pick it up in central NJ?
I have not done a front clip but played with my front mount frame etc. Make sure you have car sitting on its wheels as it will flex a lot if on stands!! If you need it on stands put them at rear most of frame and at front spring area to simulate wheels on. good luck with it all. will have to do mine one day.