If I was starting from scratch, hands down a junkyard magnum 5.2/5.9 with a supercharger or turbocharger. 500+hp for pennies on the dollar compared to a comparable n/a SB or BB.
You know I gave this serious consideration - and may give it more consideration - but what initially scared me away from a turbo is the potential for turbo leaks in the piping and how in general more complexity = more problems.
That said, with 5-10psi boost on a 5.9 Magnum, even without an intercooler, that should be a 550hp motor.
I can't see a supercharger kit being cheaper than building a N/A big block though... I could be wrong of course.
The engine I bought for my '68 Dart was an LA 360 (9:1 compression) out of a cop car from the 70's (apparently). It supposedly had a very mild rebuild in the 90's and was put in a Valiant. Sometime around 2008 the owner of the engine put a Paxton supercharger on it. The supercharger only made 4-5 lbs of boost but made 390 whp to the wheels. When I bought the engine, I first decided to send it to a machine shop to check as it had some leaks here and there and had kind of low compression on one of the cylinders. When he tore it apart he was shocked to see it had stock internals. When he checked the bores they were 0.003" out of round. I do feel like the engine did take a tole with the extra boost and hard running towards the end of its life.
Well, my engine builder and I talked it over, and for my application (someone who plans on autocrossing and road racing) we decided to go with a mild 408 stroker engine for the lighter weight, simplicity, and to free up more room in the engine bay. He projects it to make about 500-575 crank horsepower.
What I'm going to do with the supercharger? I'm either going to save it or sell it to recoupe my money. I had an interesting junkyard 273 I wanted to build or I thought it would be cool for a pre-75 small block truck as a tow rig I think the A-bodies really benefit from small blocks, but I will admit a big block does look cool in one.
If I was starting with a completely clean slate, I'd hands down go with a Gen III Hemi. If you really want to be different and have the patience with fabrication and tuning you could try doing an SRT4 swap.
