A tunnel ram can actually be very effective on a street car. It's all in the tune-up. If you decide to use the t-ram, you're going to have to be willing to invest the time necessary to properly tune the carburetors as well as your ignition timing and advance curve. It might take you a good solid week or two of driving the car around and sorting out the carbs. When it comes to tuning a set-up like this on the street, I feel it's best to start with the ignition system and get that out of the way so you can focus on the carburetion. You're going to want to lock out the distributor mechanical (and vacuum, if applicable) advance mechanisms, and run 36-38 degrees of timing all the time. You may need to invest in a start retard such as an MSD Starter Saver once you lock out the timing to help make engine starting easier & keep from damaging starters & ring gears. The 450 cfm carbs would be a decent choice, and make for easy linkage & plumbing connections since you can mount them in-line. If you have a good local carb expert that can properly modify the Holley carbs, I would strongly recommend having the air bleeds converted to screw-in style similar to what you'd find in an HP-series carb. Once you establish the jetting, power valves, and accelerator pump tuning that the engine wants, you'll find that being able to tune the air bleeds will immensely help get your combo dialed in to perfection. You may also want to consider investing in a wide-band O2 sensor & monitor, as this is an invaluable tool when it comes to dialing in an exotic induction system, especially on a street car. This all may sound like a lot, but it all depends on how successful you want the t-ram installation to be. You don't HAVE to do all this to get the engine to run or even run half-way decent, but it WILL help you get the most out of your combination. Don't be intimidated by the t-ram or pay too much attention to horror stories about how they don't make any low-end torque, they're undrivable, etc., etc.
The actual manifold choice is pretty critical as well. I've found that one of the best choices for a "street" t-ram is the entry level Edelbrock unit. It has small runners that match O.E. iron head intake port openings very well as well as most popular aftermarket heads in the 170-200cc intake runner range. The plenum design is also a bit smaller than your typical race t-ram manifolds, so air velocity is decent which will help promote throttle response and torque. The basic Weiand tunnel ram is also a nice choice for a street car, although I still prefer the Edelbrock unit over the Weiand, especially for a smaller engine like your 327.
The 4-speed transmission & 3.90 gear ratio are good choices also. Sorry for the long post!