LS swap bro! LS swap! Swap an LS! Seems to be the answer. The above image shows an LS2 swapped into a Datsun 240Z, with lots of room to spare.
This post may or may not be inspired by Datasssun's attempt towards a 5.3l LS 280z Engine swap.
So far in my largely-theoretical (at least, until the summer, maybe, cross your fingers!) quest for the ultimate budget screamer, I've examined Some Ford blocks, some low-stroke Dodge Blocks, and the possibility of building an gen I based Chevy 302, as well as toyed around with the idea of an LT1-based 302 or 327. Both are possible, but I've decided to apply the same idea to LS-based engines, which are known for being unusually high RPM V8s to begin with, especially with their hydraulic cams.
I lament the lack of a wide-bore Ford Modular engine, but the LS engines have shown that there is still life in a pushrod block.
"Vintage Displacement and Modern Technology combine for Great Performance"
GM has their own LS 327, called the (very creative) name of "LS327". But with tiny valve sizes (1.8" vs the standard 2 or 2.2") low compression (9.5:1 vs 10:1) and very narrow bore, it's a bit of a sham compared to the original 327. I think we can do better.
Due to the bad reputation of the L92, and the high cost of the LS3, let's base the engine on an LS2 block, which has 4" bore, slightly lower than the LS3's 4.06, but identical to the original 327. The LS3 is also significantly more expensive. However, if you want to use the L92 (which, someone more knowledgeable than me may be able to explain the exact differences) you can save yourself about $2000. However, it may cost that much more to bring the truck engine to spec. This would involve deleting the cylinder deactivation and adjusting the variable valve timing, though.
It's an all-aluminum engine with iron sleeves, making it very lightweight (50 lbs less than the 240Z's stock L24) for its size. Most LS engines are a head and cam limited, meaning that it is known for being able to reach much higher RPMs than is within its powerband. A standard LS2 will stop making power at 6500rpm (the redline for most LS2s) but have been known to take 7200rpm without damage regularly. Plus, unlike the other examples I've looked at, the LS2 block can take boost and 800+ HP without needing an aftermarket casting, making it a much cheaper long-term solution than the previously examined parts. It also has a bolt-in swap kit available, just like the SBC and LT1.
The LQ9 aluminum heads, thanks to their large rectangular port, when ported can have flow numbers the touch 300 @28" water on the intake side, making them suitable for most builds below 600HP, plus, slightly lowering the compression ratio allows forced induction, the ability to run lower-end gas, or (in our case) the ability to run a longer 6.275" rod to get a better rod/stroke ratio. This means that they are, generally, better than some aftermarket heads. Best of all, they can cost less than LS2 stock heads, and way less than aftermarket heads.
Here's the build with some generic cost estimates:
Chevy 5.4l "327" Hybrid (Actually 328 ci, but who's counting?)
GM Gen IV LS2 Aluminum Block ($5000)
GM Vortech LY2 Crank (3.27" stroke) ($400) + rebalanced for LS2 pistons
GM Vortech LQ9 Heads (wide, rectangular port) ($300)
GM Vortech LY2 Connecting Rods (6.275") ($200)
LS2 stock pistons (1.34" compression height, no dome) ($0)
Sell LS2 cam, intake, exhaust, heads, valves, crank, and connecting rods: (+$3500)
High-RPM solid roller Cam, springs, and valves: $2000
Ported LS2 intake: $100
Exhaust manifolds for higher RPM use: $300
Deck Height: 9.24"
TDC: .01" above deck
Compression ratio on Gen IV LQ heads, 0.03" gasket, flat LS2 Pistons: 9.96:1
4350ft/min mean piston speed (max for the 6.0 block stock) at: 8000rpm
Rod/Stroke ratio: 1.92
Bore/Stroke ratio: 1.23
Peak power estimate (with properly timed cam, intake, and exhaust:) 7500rpm
HP estimate: 480HP @ 7500rpm, around 400 ft/lbs torque between 4000 and 6000rpm.
If we assume a similar VE as the LQ9 has at its peak power of 332HP @ 5100 rpm (in reality, it would be higher if the intake/exhaust were tuned, compression ratio is very similar) then we end up with 480HP ~7500rpm. That's over 1.45 HP per cubic inch, or 89HP / liter, all from "lego-pieces" of LS motors. That's a conservative estimate, if you can manage VEs closer to other decently modified engines, you'd hit closer to 500HP.
So at the end of the day, this theoretical build has you spend about the same amount of money on a stock 400HP LS2, and comes out with a 500HP high-RPM engine that would be more controllable in a lightweight car, for about the same cost thanks to GM's part sharing and the wonders of supply and demand. Best of all, it's nearly 50% more powerful than GM's own LS327 for the same cost.