Engine/Drivetrain in Custom Built Car

I stumbled onto AF a few days ago and have been reading up on some posts. I'd have to say out of all the boards that I'm a member of, this is by far the most deverse group. I'm sure that I'll be able to learn a lot from everyone here. On to my question. I hope I posted this in the right place. It was either this, or the street racing section...

I'm working on a project to build a car from the ground up - space frame, fiberglass body etc. Until now I have settled on using a SBC for my engine (cost, availablity of aftermarket add-ons etc). I've also recently considered the rotary, although it is a little pricey I like the fact that it's high-reving and not as mainstream.

Application:
* 2 door, rear engine, RWD GT style car
* used as a weekend cruiser / occasional 1/4mile drag. Basically fast enough so I won't be laughed at on the track but reliable enough that I can use it on the street. 12-13 sec 1/4miles would be ideal
* target weight is 2200-2500lbs (or so)
* my budget for the drivetrain (engine/tranny/clutch) is about 10K.

I've ruled out the v12's (BMW and Jag) because of the cost vs performance issue. I've looked at a lot of 400-450HP chevy crates and they look ok even though they seem to be overused (no offense). Truthfully I know even less about the Ford small blocks or 5.0s. Everytime I *think* I know what will work the best, someone comes in gives me another idea. The other day I was considering a 3800 super/turbo or 3400 DOHC. The hp/wt ratio on those were nice, but I don't think I could invest all the money it takes to pull 425HP.Also, the Caddy N* is nice because I could use the computer for the a/c and stuff but it doesn't have as many add-ons; plus the price to get up the HP is a little high. ASomeone else recentlly suggested a Buick GN. Lastly, I haven't mentioned any import engines, but that's just because I know virtually nothing about them. The WRX setup looks nice but but I don't know if a 4cyc will do it for my weight.

So finally my question:
What engine setup would be best for this?

My front runners are:
Buick GN
SBC
Maybe - BMW V8

Thanks in advance,
Filip

Some suggestions to look at (I have no idea about cost in US):

Lexus 4.0 litre V8 Quadcam - I've seen one modified with small twin turbos (one per bank) intended for a GT40 replica.

3SGTE - Two litre DOHC iron-block used in Celica GT-Four and MR2 responds well to increased boost, custom manifolds but you'll need cams, pistons and rods.

LS1 or GenIII Chevrolet alloy push rod V8 - this is lighter than the traditional iron-block and can be tuned NA. Callaway is doing mods for Holden in Australia on a small-volume production basis to 300kW with complying emissions and driveby noise.

Liberty 2.0 DOHC Twin-turbo - the WRX engine's big brother makes about 209kW standard, has the advantage of having a 4WD drivetrain which may suit your application.