I need schooling - old vs. new engines

MopaR&D said
There's a point where that doesn't work out so well, I'd say around 600 HP. At that power level you're pushing the limits of a garden-variety LA block (and need thousands in aftermarket heads, cam, intake, carbs) and to get the 25+ MPG you'd need to "cobble" in some kind of overdrive trans which you'd have to do for a G3 Hemi anyway. G3 6.4L can hit 600 HP with a big cam and CASCAR intake, no need for head work or internals. So at that point it's kind of a wash, either dump money into a max-effort pump-gas SBM or dump money into parts to swap a new Hemi. And if you go with the Hemi there's far more potential power to be had.

With that said I have a 2014 5.7L sitting in storage but the 450-hp 5.9L Magnum/LA runs so well in my Duster I currently have no reason to swap. That engine has Cometic head gaskets and head studs plus factory Magnum short blocks are known to safely handle ~15 psi of boost so when I'm ready for more power it's simply a matter of bolting on a Procharger. On the topic of carbs as well, the engine currently runs fantastic with the 750 cfm Street Demon but when I'm playing with boost I'm gonna want EFI and electronic timing control. Yeah blow-through carb would work but I want that closed-loop AFR management too where I don't need to change jets when the weather or altitude changes.

I'd buy a modern Hemi car if they didn't all weigh as much as an old C-body or more. Just going off wheelbase and weight that's basically what a modern Challenger is, a 2-door C-body with 12" taken out of the wheelbase. They're friggin yuge and it really bums me out. I watched a video of a guy on YouTube who swapped a stock 6.4L SRT Hemi into a Duster with a T-56, since it's about 800 lbs lighter than a modern Challenger that car is as fast as a stock Hellcat with 200 less HP naturally aspirated and reliability of a factory-stock engine.

I'm not talking 600 hp, to me that is ridiculous. When I was younger and had all the time in the world we souped up everything from 170 cu in Plymouth's and Fords to Chrysler big blocks. They were all a blast to drive. My daily driver was a Hurst shifted, 4 speed, 64 Barracuda, 273 with about 300 hp that started and ran like it was FI. That was in the 70's and got mid 20's steady highway cruising. Want to burn rubber, spend an hour and swap gears to 4.10's. My 2009 Challenger R/T 6 speed manual gets 28 mpg. My 383 auto 68 Cuda gets high teens steady cruising on the highway. No mystery, efficiency goes up and you get the best of both worlds, FI or not. I don't even run heads past 1971. I run factory Carter carbs, a MP chrome box and distributor, and solid lifter cams. Are you faster, probably, but I already figured out I'll never have the time or money to play that game. Street only, fast, handles well, stone axe reliable is what I build for. No special parts, no computers, no cutting, just good machining and quality parts. I have always had one since I was 19, and that was 48 years ago. That is what A Bodies do best. The 2009 Challenger rolls easy and is very quiet, great car, but they are two different animals. I put more miles a year on the 66 Barracuda.