do you have any flow figures on the heads?
110885-10 NA 278 278 225º 225º .525 .525 110º 106º
2000-5800 Fair idle, Street high performance. 2200+ stall, aftermarket intake and headers
start around here and make adjustments for head flow/personal preferance,and maybe change to split patter if the exhaust flow numbers are weak compared to intake side.