Steve, don't lose site of the quote above. I know "budget" means different things to different people, but it's easy to get carried away.....I know you have some different threads for separate parts of the car, but if the "budget" is to be considered, you really need to look at all aspects. I'd hate to see you get 25k+ deep in a Valiant that you'll be tired of in a year or two.
You really need to ask yourself, is this a build that i'll really love, will keep for years, and upgrade power in the future? If not, i'd take the milder route for now.
Since your talking rear suspensions and budgets, for long term durability, you may want to consider housing choices while you're at it. 10 oh's is approaching, a back braced/fabbed 8 3/4, Dana 60, or even 9" Ferd territory.
As I mentioned above for this particular thread, the housing needs consideration. Add the cost of a 500/600hp plant that has some modicum of reliability, a good trans/converter, plus all the other essentials like the fuel system, cooling, wiring, hardware, etc. It will become costly in a big hurry.
Good luck with the project. Have fun, but really step back and look from time to time to make sure your plans really meet your goals.