I currently am running a 289 with performer rpm heads (1.90" intake) in a 67. Im running a turbonetics 62-1 with .81 turbine. For this winters upgrade, i have a budget which is roughly limited to either buying a used 331 stock block with studs and girdle with victor jr heads from my buddy, or building my own all new shortblock. I was interested in a 363 for future upgrades, but i dont know if i am worse of running my current heads. Supposedly the larger bore unshrouds the valves for better flow, but I am not sure how much. Right now i push about 12 psi non IC with water meth. For street driving, just looking for better low end. I am running a performer rpm hyd flat tappet cam, so a roller is definitely going in. I thought about added a roller to my current engine, but only seems like a matter of time till it dies. Been two seasons of beating so far, still running fine, it just runs out of steam at 5500 rpm. Thanks for the feedback if you have any advice.