DEFINATELY would feel the difference. I used that same cam in a boat, and it runs GREAT! Boats pull really hard through the entire RPM band, and that cam makes great low end power and maxes out at 4800RPM in my setup (would only run 4200 max with the 350). I think you could go a bit bigger cam in a car, but certainly that cam would be "safe" as far as low end power and a great idle. You can always get by with a little bigger cam with more cubes. I didn't think the expense was that much more for the 383. The extra machine work is minimal, you have to buy new pistons anyway when you bore a motor (asuming you are boring it). The only thing you need is a 383 crank, and some 5.7 rods, an externally balanced Harmonic balancer and flexplate. You could actually get all that stuff out of a 400, but assuming you have no 400 laying around, you can buy them from Scat for $500-$700. You can get by with 4130 I beam rods with the low RPM motor you are building. 6 inch rods are expensive and H beam rods are expensive but you don't need them for your motor. Scat also sells an internally balanced 383 crank, they are a little pricey, but you could use your stock balancer and flexplate.