Why are people so confused saying that LS parts cost more? You can get a nice, lower mileage 5.3 from any junkyard for $500ish, most are even cheaper. You will already be making more then any 350 could dream of on a stock cam. Do a decent cam and headers, and you are leaps and bounds away from a regular SBC. Not to mention it is fuel injected, so you can start it up whenever, and get much much much better mileage.

Trust me, there 454 will make you not want to drive it because of gas mileage. Why would you do anthing else when you can make 400 RWHP and still get 20+ mpg, saying that you do a 4l80e/ 4l60e as well. Heck, a stock 5.3 with a good stall will get you into the 13s/ high 12s.