What should I do?

The biggest issue is it's a V8. It takes more to rebuild a V8. Any V8...lol. So the fact it's a 273 has no bearing on the cost. The 383s and 273s suffer from a lack of decent piston choices. The best way to get power is compression, and more so with a small displacement. I would plan to keep the closed chamber heads but have a performance vave job done. I'd go with custom forged pistons because I can get what I want in any size, and they will never get hurt. But, that's a set of $700 pistons. You'll have easy $4K into byt the time it's running. Up grade the pistons, upgrade the cam, and you will easilly make 300 horsepower. Whether it can be done for $3K is another matter, and I'm inclined to say no. A stock rebuild, sure. but not a performance engine that has to make 1.1 horsepower per inch.