Cheapest way to built a 300-350hp small block

Response is good, been there done that.

For your goal if 300 or better HP on a stock 360/low compression, do this;

Open air cleaner up top a 650 AVS or Holley carb. A TQ is also good to use. A small primary unit is what I would look for.

Any basic 4bbl. intake. Iron ones are mostly over priced while Edelbrock Performers can come inexpensively. The Weiand Action Plus is also a excellent choice.

Keep the stock heads as is. A mild milling is a plus but mandotory.

Headers help a lot. Use a 2-1/2 pipe.

Cam; with 3.55 gears and a stock tire, a cam of approx. 228intake duration will work. Use a split duration cam (more exhaust duration.) to help the engine get rid of the exhaust gas and extend the RPM range.

I would not exceed a cam intake duration of 228/230 degrees.

If your not going to get a converter to aid the set up, cheat and use Rhodes lifters. Skip the roller cam. Roller lifters are nice but a expensive gain for little power returned.