273ci thoughts?

A 273 build is gonna get you between 250-350 hp depends what you do. Stock heads with high CR and 280 ish cam 4bbl and headers would be about 300 hp, port heads or better heads and get about 350 hp possibly more. Go more mild cam and CR be about 250 hp. Main problem with 273 is gonna need at least full rear gear ratio lower than a similar built 360 to get similar performance. Eg. a 360 with 3.23, 3.55, 3.91 would be 4.30, 4.56, 4.88 with a 273 plus probably a 1000-1500 or more stall over a 360.
If your willing to gear then build it if not go with bigger displacement.