Yes 360 would make the most sense it has the best compromises for it CID with bore/stroke and rod ratios but at the same time as you say that I shouldn't run my 273 cause its 80+ smaller I could say why would you not run a 440 cause its 80 cubes bigger. For the Hp and rpms I want 273 fits for me plus its alittle more for a challenge to build a strong running 375-400hp 273 than a 360.