I have spoken in person to all the Weavers at Unique. Give them a call if you like. Very helpful people. Bob Putnam from ERA is lurking around here some where. Great guy. Dave and Tom Kirkham are also on here, another set of terrific guys. All have an outstanding reputation for quality and customer service. To me these cars represent three different price points. Hard to go wrong with them.
As for a 427 or 289? Your choice. 427 is more in demand but the FIA car is more unique.
Motors and trans. I hear lots of good about Southern Automotive. Seems to me Unique has a deal through Roush (another excellent shop). Trannies, try David Kee. There are many good shops around, this is just names I have heard over and over again....... and to the best of my recall, all positive.
Big decision with thousands of variables, take your time. There are MANY manufacturers out there. These are but a few. You stated you wanted a 'kit' so I purposely left out companies that normally deliver a 'turn key minus' or arrange to deliver a finished type of car. Although I am sure companies like Kirkhams (VERY nice) would accomidate your request. Many of the manufacturers will accomidate virtually any level of finish.
Companies like Unique and ERA have been around for a long time. Unique I think is going on its 28th year as a builder and was a restorer before that. My Unique (in my gallery), is over 18 years old. Not a single problem.
Try
www.google.com or the search function here to find links and more information.
Rick