The head is the biggest weakest link.
Stock flow from what I understand is 135 cfm which is pretty bad especially since the total flow of a 6 over an 8 gonna be less since you have two less ports. If you take the 2 x head flow cfm rule for 8 which takes a big cam and CR. Since /6 has two less ports have to modify the rule so 135 x 6 = 810, 810 รท 8 = 101cfm. So 200 hp is max available power and with a more mild cam and CR 170-180 becomes the max unless you port the heads and depending on the results you could get around 1:1 hp per cid.
Even a fully built race /6 it's hard to break 300 hp so unless you add a turbo go v8 even a 273 could hit your power goals without trying. And don't forget about torque a 225 hp 360 with 3.55 you'd need a 225 hp /6 with something like 5.56 gears to equal it up lol.
